Seppo Niemi

The first generation biodiesel: The effects of raw material on physical properties, oxidation stability and emissions

The aim of this study was to compare oxidation stability, emissions during engine tests and fuel properties of biodiesels. The biodiesels were produced from different raw materials using the transesterification process. The raw materials used were: salmon oil, fox fat, rainbow trout oil, rapeseed oil and linseed oil. The engine tests showed differences in emissions with different biodiesels. The fatty acid profiles were measured and their effect on oxidation stability and other fuel properties were noticeable. The effect of synthetic antioxidant was also measured for different biodiesels. The oxidation stability increase was related to the raw material used to produce the fuel. The oxidation stability of biodiesel blends was measured. The oxidation stability of the blended fuel increased when biodiesel with a higher oxidation stability level was introduced. These measurements indicate that oxidation stability can be enhanced with antioxidants and by blending diesel fuel or other biodiesels together.

Results of an Off-Road Diesel Engine Driven With Different Animal Fat Based Biofuels

The demand for increased use of biofuels in both on- and off-road diesel engines is growing. The carbon dioxide emissions must be reduced, but the increase in the petroleum prices and possible shortage of crude oil also promote the interest in biofuels. Simultaneously, exhaust pollutants of diesel engines have to be drastically reduced. The nitrogen oxides (NOx ) and particulate matter (PM) form the main challenge for diesel exhaust cleaning. Despite the emissions reduction, the fuel economy of the engines should be kept at a sufficient level to also prevent the CO2 increase. In the present study, a turbocharged, inter-cooled direct-injection off-road diesel engine was driven with two animal fat based bio-fuels, namely steelhead (or rainbow trout) methyl ester (StME) and crude steelhead oil (StO). Crude or neat biofuels are also of interest since medium-speed engines are able to burn unrefined bio-oils. A vegetable oil based fuel, canola oil methyl ester (RME) served as the main reference biofuel. The baseline results were measured with commercial low-sulfur diesel fuel oil (DFO). The main aim of the project was to clarify how the waste-derived animal fat based biofuels are suited to engine use. The performance and emissions characteristics of the engine were determined. In addition to regulated emissions, the particle size distributions were also examined. The results showed that the studied animal fat derived ester was very suitable for the off-road test engine. NOx increased but hydrocarbons (HC), smoke, and PM mass decreased (by up to 60%) while thermal efficiency and carbon monoxide (CO) remained approximately unchanged. The particle number emissions were competitive relative to DFO. Raw fish oil StO reduced HC emissions but increased NOx and particle mass and number emissions. CO and smoke behaved ambiguously, so further investigation is needed for this fuel.Copyright

Exhaust Emissions of an Off-Road Diesel Engine Driven With a Blend of Diesel Fuel and Mustard Seed Oil

In the near future, crude oil based fuels must little by little be replaced by biofuels both in the region of the European Union (EU) and in the United States. Bearing this in mind, a Finnish-made off-road diesel engine was tested with a biofuel-diesel fuel blend in the Internal Combustion Engine (ICE) Laboratory of Turku Polytechnic, Finland. The biofuel was cold-pressed mustard seed oil (MSO). The engine operation, performance and exhaust emissions were investigated using a blend of 30 mass-% MSO and 70 mass-% diesel fuel oil (DFO). The injection timing of the engine was retarded considerably in order to reduce NOx emissions drastically. The main target was then to find out, whether the blended oxygen containing MSO would speed up the combustion so that the particulate matter (PM) emissions would remain unchanged or even decrease despite the injection retardation. As secondary tasks of the study, the NOx readings of the CLD and FTIR analyzers were compared, and exhaust contents of unregulated compounds were determined. Retarding the injection timing resulted in a significant decrease of NOx emissions, but in an increase in smoke, as expected. At retarded timing, the NOx emissions remained almost unchanged, but the amount of smoke decreased when the engine was run with the fuel blend instead of DFO. At retarded timing at rated speed, the number of ultra-fine particles decreased, but the amount of large particles increased with DFO at full load. At 10% load, however, the particle number increased in the entire particle size range due to retardation. At both loads, the use of the fuel blend slightly reduced larger particles, whereas the number of small particles somewhat increased. At full load at an intermediate speed of 1500 rpm, the PM results were very similar to those obtained at rated speed. At 10% load with DFO, however, the injection retardation led to a higher number of larger particles, the smaller particles being at almost an unchanged level. With the fuel blend, the particle number was now higher within almost the whole particle diameter range than with DFO. Considerably higher NO2 contents were usually detected with FTIR than with CLD. The shape of the NOx result curves were rather similar independent of which one of the analyzers was used for measurements. The NOx contents were, however, generally some ten ppms higher with FTIR. The exhaust contents of unregulated compounds were usually low.Copyright

Crank Shaft Torsional Vibration Analysis on the perspective of Improving the Crank Angle Measurement Accuracy for Closed-loop Combustion Control in ICES

Crank shaft torsional vibration has impact on the crank angle measurement accuracy in large-bore Internal Combustion Engines (ICE). In large bore engine, the torsional vibration angular displacement can be up to 1 degree, which in turn can cause a fault of 2 bar in Indicated Mean Effective Pressure (IMEP) and a fault of 0.6 degrees in the Crank Angle of 50% burned (CA50). IMEP and CA50 are critical feedback parameters for closed-loop combustion control, therefore to compensate torsional vibration effect in real-time engine control system can not only provide higher accuracy crank angle data but especially improve the combustion analysis and closed-loop control accuracy. Thus, in this work, a torsional vibration dynamic model is established to improve the accuracy of the crank angle measurement. A lumped parameter model of torsional vibration is established for a Wärtsilä engine, the numerical computing method is determined, harmonic analysis is applied, the Transfer Matrix Method (TMM) result is verified with flexible Multibody Simulation (MBS) calculation and the accuracy of the torsional vibration model is estimated. For the trial of online crank angle correcting, the computation time of this model was found to be around 300 to 400 times heavier as IMEP calculation. A direct IMEP correcting model based on a linear dependence of cylinder number with an accuracy of ±0.1 bar compared with the reference was proposed. Based on all those results, it is concluded that the TMM method can calculate the angular displacement from torsional vibration with high accuracy and correct the crank angle measurement from cylinder-wise and crank angle wise, and the torsional vibration calculation resolution needs to be considered based on performance and calculation capacity. Introduction For a dynamic running engine, torsional vibration is one of the greatest threats for crankshaft over loading [1, 2, 3, 4]. Research about the torsional vibration have been developed since the 1950s [1, 4]. The applications of using torsional response for engine combustion diagnosis have been mostly relying on the flywheel speed measurement for engine misfiring detection [5, 6, 7, 8], cylinder pressure reconstruction [9, 10], engine roughness criteria development [11], and IMEP and HRR estimation [12]. Additional work have been published about the torsional vibration analysis, for example: practical methods to reduce torsional vibration [13, 14, 15], system nonlinear dynamics [16], model simplifications [17, 18] and coupled torsional, longitudinal and bending vibrations [19, 20, 21], and transient torsional vibration response [22]. However, regarding online crank angle correction, so far according to the author’s knowledge, there is not much work done. Therefore in this work a preliminary study of the online crank angle correction is done. Torsional vibration is caused by the periodic and uneven excitation torque in each crank pin, and it leads to different angular velocities or displacements from this oscillating torque in the shaft. Out of many excitation torques acting on the crank-rod system, the tangential component of the piston force is the excitation force for crankshaft torsional vibration [1, 16, 23]. Moreover, torsional vibration is the most significant error contributor for crank angle measurement system [24]: torsional vibration of a 10 cylinder V-engine can have up to 0.4 degrees error in crank angle measurement. Therefore, a further research about the torsional vibration phenomena and its feasibility of correcting the crank angle measurement error online is carried out in this work. Crankshaft modelling is the base of crankshaft torsional vibration analysis. Practically, there are three most basic shaft models used for torsional vibration analyses: simple mass -

Analysis of Cylinder Pressure Measurement Accuracy for Internal Combustion Engine Control

With the tightening requirements on engine emission and performance, pressure based combustion controls are becoming common in medium speed large bore reciprocating internal combustion engines. The accuracy of the cylinder pressure data including the raw pressure value at its corresponding crank angle, has a vital impact on engine controllability. For instance, this work shows that a 1-bar pressure offset leads to a 0.7% variation in the total heat release (THR) while the 50% heat release crank angle (CA50) can be shifted by 2 degrees. Similarly, with a single degree error in the crank position, the indicated mean effective pressure (IMEP) gets a 1.5% error. Thus, in this work the typical errors for cylinder pressure measurement are reviewed and analyzed for large bore four stroke marine and power plant production engines. The main sources of error for pressure measurement are thermal shock and installation defects. Meanwhile, calibration is carried out for ten production pressure transducers to provide a general accuracy result of the pressure transducers that are used in production engines. The main sources of error for crank angle position monitoring when done with a flywheel-based inductive system, manufacturing tolerance, installation, and the relative displacement between the pickups and the shaft due to shaft bending, shaft longitudinal movement, torsional vibration and engine block vibration are the main sources of error. In this paper, those errors are quantified individually through simulation and their impacts on IMEP and CA50 are also presented. At last, cylinder volume deformation and its impact on combustion diagnostics are also estimated. From the result it is concluded that torsional vibration and cylinder volume deformation have the most significant effects for combustion analysis.

Injection Pressures of a Bio-Oil Driven Non-Road Diesel Engine: Experiments and Simulations

The depletion of global crude oil reserves, increases in fossil fuel prices and environmental issues have encouraged the search for and study of bio-derived fuels. For years, fatty acid methyl esters (FAME) have already been used successfully. High-quality hydrogenated vegetable oil and Fischer-Tropsch biofuels have also been developed.Fuel refining processes, however, consume energy increasing CO2 emissions. For profitability reasons, large-scale industrial production is also required. Several distributed energy producers are instead willing to utilize various local waste materials as fuel feedstock. The target is local fuel production without any complicated manufacturing processes.Crude bio-oils are therefore also interesting fuel options, in particular for medium-speed diesel engines capable of burning such bio-oils without any major problems. Nevertheless, waste-derived crude bio-oils have also been studied in Finland in high-speed non-road diesel engines. One option has been mustard seed oil (MSO). Mustard has been cultivated in fallow fields. Non-food mustard seeds have been used for fuel manufacturing.In the performed studies with MSO, the exhaust smoke and HC emissions decreased, NOx remained approximately constant, and the thermal efficiency was competitive compared with operation on ordinary diesel fuel oil (DFO). The number of exhaust particles tended, however, to increase and deposits were formed in the combustion chamber, particularly if the engine was also run at low loads with MSO. On the whole, the results were so promising that deeper analyses of engine operation with MSO were considered reasonable.The kinematic viscosity of crude bio-oils is much higher than that of FAMEs or DFO. Consequently, the injection pressure tends to increase especially at the injection pump side of an in-line injection pump system. The flow characteristics of crude bio-oil also differ from those of DFO in the high-pressure pipe. With bio-oil, the flow seems to be laminar. The bulk modulus of bio-oils is also different from that of DFO affecting the rate of the injection pressure rise.In the present study, a turbocharged, inter-cooled direct-injection non-road diesel engine was driven with a mixture of MSO (95%) and rape seed methyl ester (RME, 5%), and standard DFO. The engine was equipped with an in-line injection pump.First, the injection pressures at pump and injector ends of the high-pressure injection pipe were measured for both fuels as a function of crank angle. Furthermore, a model was created for the injection system based on the method of characteristics.Free software called Scilab was adopted for numerical simulation of the model. Despite a few limitations in the built model, the results showed clear trends and the model can be used to predict changes in the fuel injection process when the fuel is changed.Copyright

Particle Number Emissions of Nonroad Diesel Engines of Various Ages

Over the last two decades, gaseous and particle mass emissions of new diesel engines have been reduced effectively and progressively in response to the emissions legislation and due to the applied new technologies. There is, however, increasing concern about whether the engine modifications, while improving combustion and reducing emissions, have increased the number emissions of ultrafine and nanoparticles. So far, emissions regulations have solely been based on particulate matter (PM) mass measurements, not on particle number. Nanoparticles, however, form a major part of the PM emissions, but they do not considerably contribute to the PM mass and cannot be seen as a problem, if only PM mass is determined. Therefore, there is increasing interest in expanding the scope of the regulations to also include particle number emissions, e.g., Euro VI for on-road engines. The PM number limit will also be enforced for nonroad engines slightly later. Thus, more information is required about the particle number emissions themselves, but also about the effects of the engine technology on them. Wall-flow diesel particulate filters reduce the particle number very effectively within the entire particle size range. Nevertheless, in order to keep the filter as small as possible and to lessen the need for regeneration, the engine-out PM number should also be minimized. If the diesel particulate filters (DPFs) could be left out or replaced by a simpler filter, there would be greater freedom of space utilization or cost savings in many nonroad applications. This might be realized in installations where the engine is tuned at high raw NOx and a selective catalytic reduction (SCR) system is adopted for NOx reduction. However, it is not self-evident that new engine technologies would reduce the PM number emissions sufficiently. In this study, particle number emissions were analyzed in several nonroad diesel engines, representing different engine generations and exploiting different emissions reduction technologies: four- or two-valve heads, exhaust gas recirculation, different injection pressures and strategies, etc. All engines were turbocharged, intercooled, direct-injection nonroad diesel engines. Most engines used common-rail fuel injection technology. Comparisons were, however, also performed with engines utilizing either a distributor-type or an in-line fuel injection pump to see the long-term development of the particle number emissions. In this paper, the PM number emissions of nine nonroad diesel engines are presented and compared. Gaseous exhaust emissions and fuel consumption figures are also provided.

Particle Number Emissions of Non-Road Diesel Engines of Various Ages

Over the two last decades, gaseous and particle mass emissions of new diesel engines have been reduced effectively and progressively in response to the emissions legislation and due to the applied new technologies.There is, however, increasing concern about whether the engine modifications, while improving combustion and reducing emissions, have increased the number emissions of ultrafine and nanoparticles. So far, emissions regulations have solely been based on particulate matter (PM) mass measurements, not on particle number. Nanoparticles, however, form a major part of the PM emissions, but they do not considerably contribute to the PM mass and can not be seen as a problem, if only PM mass is determined.Therefore, there is increasing interest in expanding the scope of the regulations to also include particle number emissions, e.g. Euro VI for on-road engines. The PM number limit will also be enforced for non-road engines slightly later. Thus, more information is required about the particle number emissions themselves, but also about the effects of the engine technology on them.Wall-flow diesel particulate filters (DPFs) reduce the particle number very effectively within the entire particle size range. Nevertheless, in order to keep the DPF as small as possible and to lessen the need for regeneration, the engine-out PM number should also be minimized.If the DPF could be left out or replaced by a simpler filter, there would be greater freedom of space utilization or cost savings in many non-road applications. This might be realized in installations where the engine is tuned at high raw NOx and an SCR system is adopted for NOx reduction. However, it is not self-evident that new engine technologies would reduce the PM number emissions sufficiently.In this study, particle number emissions were analyzed in several non-road diesel engines representing different engine generations and exploiting different emissions reduction technologies: 4- or 2-valve heads, exhaust gas recirculation (EGR), different injection pressures and strategies, etc. All engines were turbocharged, intercooled, direct-injection non-road diesel engines. Most engines used common-rail fuel injection technology. Comparisons were, however, also performed with engines utilizing either a distributor-type or an in-line fuel injection pump to see the long-term development of the particle number emissions.In this paper, the PM number emissions of nine (9) non-road diesel engines are presented and compared. Gaseous exhaust emissions and fuel consumption figures are also provided.Copyright

A comparative study of the antioxidant effect on the autoxidation stability of ester-type biodiesels and source oils

The aim of this study was to compare stabilities of bio-oils and fuels that are extracted from low value feedstock (animal-based fat) to those of more conventional feedstocks (rapeseed oil). The biofuel feedstocks chosen represent the current situation of decentralized biodiesel production in Finland. The Finnish biodiesel production is based on the low value feedstocks that are mainly by-products of small-scale industry (e.g. food industry). The stabilities of these biofuels were measured by determining their Oxidation Stability Index (OSI) using the Rancimat method. The stabilizing effect of synthetic antioxidants (BHA and IONOL BF 1000) for oils and ester-type fuels used was determined. With different antioxidants, there were considerable differences between the stabilities of the oils and fats as well as of the esters made from these feedstocks.

Production of bio-oils: physical and energy technical properties

The aims of this research are to find, in decentralized production, more economical and effective techniques based on sustainable energy to extract and transesterificate oil to fuel (the use of ethanol, catalysts, and so on), to find new more effective filtering techniques to clean oils and fats for diesel fuel that produces less pollutants, verified by engine experiments, to find optimal regulations and design parameters for engines using biodiesel, to obtain real-life and laboratory test results on performance and emissions with cars and larger engines, to be able to make tests and applied research that smallscale industry and oil producers need, and to be able to produce technical information about oil extracting and transesterification processes. Some preliminary results of optimizing the seed pressing process are published here. Very first diesel engine results obtained with animal fat based biodiesel are also presented, and compared with those of rape seed methyl ester. Animal fat based bio-fuel was produced by the transesterification technique.