An Experimental Study of White Deposit Formation on IG Coil in SI Engine

<div class="section abstract"><div class="htmlview paragraph">This paper seeks to examine the effect of distance of the gas injector from an inlet valve on the combustion process in a LPG fuelled SI engine under varied injection timing. Tests were conducted at an engine test stand, where the operating conditions of the engine were maintained stable. The tests were undertaken on an indirect injection spark ignition engine under partial load and at a constant speed. Holes in the inlet pipes were drilled in order to test for four variants of injection nozzle distance from the combustion chamber into which 4 mm diameter nozzles were successively mounted. Each given distance was measured along the symmetry axis of the inlet port, which represents a real path of the fuel-air mixture.</div><div class="htmlview paragraph">The results show that the engine performance is affected more by the injector distance from the inlet valve than by varied LPG injection timing. Consequently, cycle-to-cycle variations of main combustion parameters and engine performance parameters were analyzed. The results show that the distance between the injection nozzle and the combustion chamber affects the unrepeatability of engine operation. To evaluate the cycle-to-cycle variations of the combustion parameters, the coefficient of variation (COV) and return maps of the IMEP were calculated for each engine operating condition. The increase of CO and HC emission were recorded in some cases because of the nozzle distance impact on combustion. The maximum distance between the nozzle and the inlet valve caused a significant increase of hydrocarbon in exhaust gases.</div></div>

<div class="htmlview paragraph">Motor fuels are today increasingly blended with oxygenate components to reduce global CO<sub>2</sub> emissions. Among these components, biomass-derived ethanol is very popular for spark ignition engine operation as it is not only a renewable source of energy, but it also allows to increase the engine power and thermal efficiency. Indeed, ethanol has the advantage of a high latent heat of vaporization leading to the so-called “cooling effect” which allows to increase the air-mass flow rate in the engine while reducing the charge temperature. This last property of ethanol combined with its high octane index make the engine less sensitive to knock. Then, although ethanol is characterised by high combustion speeds, optimal values of spark advance can be maintained on a larger range of engine operating conditions and high compression ratios as well as increased levels of downsizing can be used, all these aspects contributing to improve fuel consumptions.</div> <div class="htmlview paragraph">However, the real potential of ethanol blended fuels still has to be explored and their impact on engine control strategies has to be investigated, especially considering the possible fuel composition variability during the engine life. Both issues can nowadays be addressed at low cost using system simulations of the whole engine, provided that the models used correctly account for the effect of the fuel composition on combustion processes.</div> <div class="htmlview paragraph">This paper deals with the extension of a 0-dimensional coherent flame model to the combustion of ethanol blended gasoline for the simulation of heat release, knock and pollutants in SI engines. This extension mainly relies on the combination of a new laminar flame speed correlation, a modified set of chemical reactions in the flame front and an adapted correlation for the knock delay. The proposed developments are validated on a wide experimental database including many engine operating conditions as well as ethanol volume fractions ranging from 0% to 30%. Parametric variations in terms of spark advance and fuel/air ratio are also performed to compare optimal engine settings obtained from the simulations and at the engine bench. A good agreement is observed, showing the interest of using system simulations to predict the influence of the fuel composition on SI engines operation.</div>

<div class="htmlview paragraph">The production unit number of small diesel engine cars tends to decline except recreational vehicles in Japanese market in recent years, while the production unit number in Europe market keeps on increasing owing to the merits of the durability and the fuel consumption. The small diesel engines will have to be improved in the near future by solving major problems such as noise and vibration pollution, environmental pollution, improvement in performance of diesel engines, in order to expand the production of the engines.</div> <div class="htmlview paragraph">This paper refers to a basic study on the experimental and analytical methods for the reduction of resonant vibration in each vibration mode on some cylinder blocks of small high-speed diesel engines in rated engine speed range. Hammering test method, which is easy and useful for measuring frequency response functions, is carried out in the experiments. In this test, the cylinder blocks are directly excited with the impulse hammer, and more the main journals are excited via the newly-made force transmission parts in the next experiment. Two kinds of the engines which have been recently recognized as low noise and vibration engines are chosen in this study. The cylinder blocks of the engines are called of long skirt type and ladder frame type, respectively. The vibration characteristics of these cylinder blocks are obtained in the frequency range from 500 <i>Hz</i> to 2 <i>kHz</i> using the experimental modal analysis. This frequency range is chosen in consideration of the reliability of the vibration experiments. And the force transmission routes from the piston heads to the crank journals of each cylinder block are considered as mentioned in the latter experimental method. The experimental results are used to calculate the natural frequencies by the modal analysis and the calculated results are compared with the ones obtained from FEM analysis. Furthermore, the cylinder blocks are remodeled in order to reduce the vibrations of all modes using FEM analysis.</div> <div class="htmlview paragraph">Consequently, it has been shown that the vibration stress of the cylinder block can be reduced by higher rigidities and more lightening weights of the crankcase and the crank journals in the measured frequency range.</div> <div class="htmlview paragraph">The conclusions are described as follows;</div> <div class="htmlview paragraph"> <ol class="list nostyle"> <li class="list-item"> <span class="li-label">1</span> <div class="htmlview paragraph">The hammering test method using the force transmission parts is useful to measure the natural frequencies of a cylinder block. This method can be easy to get the equal results with the measured ones on running conditions without engine operation.</div> </li> <li class="list-item"> <span class="li-label">2</span> <div class="htmlview paragraph">The hammering test method using the force transmission parts can easily analyze the natural frequencies at all the vibration modes on equal conditions with running ones. Then the method is a useful tool for improving the vibration characteristics.</div> </li> <li class="list-item"> <span class="li-label">3</span> <div class="htmlview paragraph">It has been proved from the analytical viewpoints that the cylinder block of the ladder frame type can be adopted as low-noise, small diesel engines with little increase of the engine weight while maintaining higher rigidity.</div> </li> </ol> </div>

<div class="htmlview paragraph">The fuel direct injection in SI engines is demonstrating a remarkable potential regarding the reduction of consumption and pollutant emission. Nevertheless, the management of the mixture formation “in-cylinder” - in conditions of a short duration and of a complex fluid dynamic configuration imposes both an accurate modeling and an exact control of the process.</div> <div class="htmlview paragraph">The problem gains on complexity when considering the use of alternative fuels which becomes more and more a subject of actuality.</div> <div class="htmlview paragraph">The paper presents a comparative analysis of mixture formation process and engine performances, when applying direct injection of gasoline, respectively of ethanol in a four-stroke single cylinder SI engine. The modulation of the injection rate shape is the result of a fuel high pressure wave, generated in a pressure pulse direct injection system.</div> <div class="htmlview paragraph">The internal mixture formation is modeled in base on the CFD code FLUENT, allowing the analysis of the space-and time-related process sequences for both fuels, using different parameter combinations for injection system and engine.</div> <div class="htmlview paragraph">The comparison of both fuels at the test bench of the injection system is made for different injection volumes, injection frequencies and injector opening pressures. A spray visualization for the most representative configurations is presented as well.</div> <div class="htmlview paragraph">Finally, the engine results at the test bench confirm the good adaptability of the applied direct injection concept for both gasoline and ethanol application.</div>

<div class="section abstract"><div class="htmlview paragraph">In many Asian countries a significant automobile market share is held by two and three wheelers. Generally, cost and simplicity considerations limit the performance and emission levels of small engines. Methanol is an excellent alternative fuel for SI engines due to its high-octane number, high flame speed, presence of oxygen in its molecule and thus can be used to enhance the performance of small engines. However, use of neat methanol in SI engines poses constraints due to low energy density and poor vaporization characteristics. Also, the effectiveness of methanol as a fuel has still to be thoroughly investigated in small-bore SI engines in order to assess its potential.</div><div class="htmlview paragraph">In this work, a small-bore 200cc three-wheeler automotive engine was modified to operate in the port fuel injection mode with neat methanol as the fuel. Experimental studies on the engine were conducted initially at different loads at stoichiometric conditions and performance, combustion and emissions were compared with operation on gasoline under similar conditions. The effect of air fuel ratio was also studied with the two fuels in order to identify the prospects of operating the engine with lean mixtures. The engine showed improved brake thermal efficiency and lower CO<sub>2</sub>, THC, and NOx emissions with methanol as compared to gasoline. The combustion characteristics including cycle by cycle variations have also been compared. Detailed experimental results are presented and discussed in this paper.</div></div>

<div class="section abstract"><div class="htmlview paragraph">An Air intake system (AIS) is a duct system which leads the airflow going into the internal combustion engine. Combustion requires oxygen, and the more oxygen is provided into the combustion process the more power it will produce. The lower the air temperature, the higher its density, and hence there is more oxygen in a unit volume. The quality of air entering engine can be measured with the air temperature.</div><div class="htmlview paragraph">AIS design and routing influence the air charge temperature (ACT) at intake manifold runners and ACT is normally measured at AIS throttle body in reality. Higher ACT lead to inefficient combustion and can lead to spark retard. Optimization of AIS designs and reduction of ACT can improve engine performance and vehicle fuel economy.</div><div class="htmlview paragraph">High ACT can be a result of two different phenomena: <ul class="list disc"><li class="list-item"><div class="htmlview paragraph">Recirculation - Hot air from the underhood environment ingested into the dirty side of the air intake system. This is the result of the AIS snorkel not being isolated or sealed from the engine compartment hot air.</div></li><li class="list-item"><div class="htmlview paragraph">Underhood temperature rise - Air inside AIS is heated by the ducts walls because it is routed through a hot underhood environment. The longer the length and larger the diameter of the air induction system, and the higher duct skin temperatures, the worse the temperature rise.</div></li></ul></div><div class="htmlview paragraph">In this paper, it is planned to simulate and study the effects of following factors on ACT with CFD using a FCA production vehicle: <ul class="list disc"><li class="list-item"><div class="htmlview paragraph">Snorkel location: snorkel sucking fresh air at side air guide or snorkel sucking underhood hot recirculation air.</div></li><li class="list-item"><div class="htmlview paragraph">Exhaust hot end at front of an east-west engine or at the rear of the engine; these two arrangements will result in different underhood air temperatures and radiation to AIS surfaces.</div></li><li class="list-item"><div class="htmlview paragraph">Heat shield effects on ACT: heat shield blocks radiation from exhaust system to AIS surfaces, and hence reduces charge air heat pick from AIS duct walls.</div></li><li class="list-item"><div class="htmlview paragraph">The effects of other measures such as cutting holes on hood or fenders to lower engine compartment air temperatures.</div></li></ul></div><div class="htmlview paragraph">Although the airflow in vehicle AIS duct is transient in nature, steady CFD simulations will be performed to study the above cases for simplification, and CFD approach will be discussed in details. Vehicle test data will be used to validate the CFD models.</div><div class="htmlview paragraph">Finally, general practices of AIS development will be discussed, and future work on this topic will be outlined.</div></div>

<div class="section abstract"><div class="htmlview paragraph">All internal combustion piston engines emit solid nanoparticles. Some are soot particles resulting from incomplete combustion of fuels, or lube oil. Some particles are metal compounds, most probably metal oxides. A major source of metal compound particles is engine abrasion. The lube oil transports these abraded particles into the combustion zone. There they are partially vaporized and ultrafine oxide particles formed through nucleation [<span class="xref">1</span>]. Other sources are the metallic additives to the lube oil, metallic additives in the fuel, and debris from the catalytic coatings in the exhaust-gas emission control devices. The formation process results in extremely fine particles, typically smaller than 50 nm. Thus they intrude through the alveolar membranes directly into the human organism. The consequent health risk necessitates a careful investigation of these emissions and effective curtailment.</div><div class="htmlview paragraph">Substantial information is available on diesel engine particulate emissions [<span class="xref">2</span>, <span class="xref">3</span>, <span class="xref">4</span>] but less for SI engines. Beside an example of metal oxide particles from a diesel engine, the present paper shows preliminary results of nanoparticles emissions of SI engines.</div><div class="htmlview paragraph">Four SI engines were investigated: two older and two newer engines, comprising two car engines and two motorbikes. The tests were done on standard transient driving cycles, and steady-state at constant 50 km/h and idling. Prior investigations observed, especially during idling, high concentrations of metal oxide particles [<span class="xref">2</span>]. All tests were done with particle samples collected from the CVS tunnel, during a long operating period, to have sufficient material for analyzing the composition. At the steady-state points, the particle size spectra were measured.</div><div class="htmlview paragraph">The results show that the older SI engines emit high concentrations of soot particles and metal oxide (= ash) particles. The size distribution is decisively bimodal for both soot and ash particles.</div><div class="htmlview paragraph">The newer engines' emission results are less uniform and the concentrations lower, as expected. Altogether, the concentrations of these metal oxide particles are so high, that more detailed investigations are recommended.</div></div>

<div class="htmlview paragraph">SI engines are exposed to the risk of knocking combustion if the resistance of the fuel against self ignition is too low. Knocking combustion cycles can be detected by means of the vibration signal energy calculated in a predetermined time window, Based on a continuous signal sampling during quasi-steady engine operation an appropriate data processing technique has been developed to identify the engine operation conditions which are suspected to disturb the knock detection.</div> <div class="htmlview paragraph">To increase knock detection reliability a new strategy has been developed; characteristic features are: wideband filtering of the structure vibration, window energy calculation of the signal, determination of the standard deviation of the energy values.</div> <div class="htmlview paragraph">A knock control simulation code has been written for the standard deviation strategy. Knock control system calibration can be optimized by aid of this program very efficiently.</div>

<div class="section abstract"><div class="htmlview paragraph">The paper presents a combined experimental and numerical activity carried out to improve the accuracy of conjugate heat transfer CFD simulations of a high-performance S.I. motorbike engine water cooling jacket. The computational domain covers both the coolant jacket and the surrounding metal components (head, block, gasket, valves, valve seats, valve guides, cylinder liner, spark plug).</div><div class="htmlview paragraph">In view of the complexity of the modeled geometry, particular care is required in order to find a tradeoff between the accuracy and the cost-effectiveness of the numerical procedure. The CFD-CHT simulation of water cooling jackets involves many complex physical phenomena: in order to setup a robust numerical procedure, the contribution of some relevant CFD parameters and sub-models was discussed by the authors in previous publications and is referred to [<span class="xref">1</span>, <span class="xref">2</span>, <span class="xref">3</span>, <span class="xref">4</span>].</div><div class="htmlview paragraph">Among the formers, the effects of a proper set of boundary conditions and a detailed representation of the physical properties of the involved materials were evaluated. Among the latter, the contribution of a two-phase approach taking into account the effects of phase transition within the engine coolant was considered.</div><div class="htmlview paragraph">The CFD-CHT setup is now applied to investigate and understand the origin of a critical engine behavior occurring at the engine test bench under a severe reliability test. Additional sub-models are introduced and their impact on the results is discussed. Different engine operations are modeled and a detailed analysis of the many thermo-mechanical factors influencing the engine fatigue strength is carried out.</div><div class="htmlview paragraph">At the end of the process, CFD simulations are able to correctly capture and understand the origin of the engine failure, thus leading to a faster and more effective design modification.</div></div>

<div class="htmlview paragraph">This paper presents several methods for reducing engine weight primarily through substitution with light-weight materials. The efficiency and performance of the engine were reviewed using a light-weight experimental engine (hereinafter called “weight-reduced engine”) constructed by the authors in order to investigate the possibility of practical use of the proposed weight reduction measures.</div> <div class="htmlview paragraph">The weight-reduced engine is based on an in-line 4-cylinder, 2.0 liter, gasoline engine with the base engine weight of 162 kg excluding engine oil and coolant and was reduced by 37 kg by applying alternative light-weight materiaLs and new manufacturing techniques. This corresponds to 23 % weight reduction.</div> <div class="htmlview paragraph">The materials used in the weight-reduced engine are 53 % steel, 33 % aluminum, 7 % plastics and 7 % other light-weight materials.</div> <div class="htmlview paragraph">It was found that by application of light-weight materials, the engine performance of the weight-reduced engine could be improved. That is improvements in response and friction loss. In particular, weight reduction of the major moving components, such as connecting rods, not only contributes to reduce friction loss but leads to a weight reduction for other components.</div> <div class="htmlview paragraph">The light-weight components have been put to various kind of testings which cover fatigue of components and bench testing with assembled engine by motoring and firing. These results were sufficient to confirm that these components are durable enough to operate in a practical environment.</div>

<div class="htmlview paragraph">The combustion of diesel fuel emulsions with immiscible, low-boiling point liquids, such as water and lower alcohols, presents some interesting outlooks.</div> <div class="htmlview paragraph">A study has been carried out in order to determine the effects on the engine performances and exhaust emissions of ethanol and water as internal phases in diesel fuel unstabilized emulsions - directly formed in the injection line.</div> <div class="htmlview paragraph">Using a four cylinders, direct injection, water-cooled, diesel engine fed with ethanol emulsions (at 10, 20, 30 and 40 mass percentages) and water emulsions (at 10 and 20 mass percentages), data were obtained, the engine speed varying, at full load, from 1100 to 2000 rpm.</div> <div class="htmlview paragraph">Comparison with the diesel fuel operation was made by using two different criteria: constant total energy input rate and constant total mass flow into the engine, Further experiments, varying the load and the injection timing, were also carried out.</div> <div class="htmlview paragraph">The results show that ethanol and water could replace up to 40% and 20%, respectively, of diesel fuel, while keeping the normal engine operating stability.</div> <div class="htmlview paragraph">A better thermal efficiency and an increased ignition delay were obtained by burning both kinds of emulsions.</div> <div class="htmlview paragraph">Carbon monoxide emissions, smoke and particulate mass rates were lower in emulsion - feeding conditions.</div> <div class="htmlview paragraph">Oxides of nitrogen emissions depend mainly on the internal phase amount and on the kind of emulsion and the comparison criteria.</div> <div class="htmlview paragraph">Furthermore, the use of ethanol emulsions seems to affect the size distribution of the exhaust particulate. Such aspect, however, requires additional studies.</div> <div class="htmlview paragraph">Finally, for a better interpretation of the obtained results, a simple zero-dimensional thermodynamic model of the engine cycle was developed.</div>

<div class="htmlview paragraph">The method of fatigue life evaluation and validation testing under operational conditions is a prerequisite to achieve optimal designs with respect to weight and long-term durability of the structure considered.</div> <div class="htmlview paragraph">Criteria like driving behavior and braking performance, influenced by global stiffness as well as fatigue life evaluation were taken into account when optimizing a forged 6.5 front axle beam of a heavy truck. The procedure for weight optimization includes the following steps: <ul class="list disc"> <li class="list-item"><div class="htmlview paragraph">Stress analysis e.g. using strain gage techniques and/or Finite Element Method,</div></li> <li class="list-item"><div class="htmlview paragraph">Road load data acquisition and derivation of design spectrum describing customer usage,</div></li> <li class="list-item"><div class="htmlview paragraph">Fatigue testing under constant amplitude and/or variable amplitude loading to establish component related SN-curves and/or fatigue life curves,</div></li> <li class="list-item"><div class="htmlview paragraph">Fatigue life evaluation using damage accumulation hypothesis (Miner's Rule),</div></li> <li class="list-item"><div class="htmlview paragraph">Optimization and weight reduction (in this case 14% weight savings were achieved) based on fatigue life evaluation.</div></li> <li class="list-item"><div class="htmlview paragraph">Validation testing using multi-axial computer controlled, servohydraulic test rigs.</div></li> </ul></div> <div class="htmlview paragraph">Since vehicle manufacturers tend to leave more of the development responsibility to the component manufacturer, the methodology described is directed to the component manufacturer and is condensed, introducing the “service strength evaluation diagram” used for design optimization. Using this technique a designer can get a good feel for the relative impact of design changes with respect to durability life under service conditions.</div>

<div class="htmlview paragraph">Dimethyl Ether (DME) is a promising new alternative fuel for compression ignition DI engines. However, some problems arise from the poor lubricity of DME. Breakdown of the film bearing between needle and sleeve of the injector can lead to mechanical wear and leakage, a problem that is not mitigated easily. For example, the application of returning the leakage to fuel tank could raise a back pressure on the injection needle. This pressure can affect injection rate and consequently engine performance.</div> <div class="htmlview paragraph">In this study, fuels based on various DME to gas oil (diesel fuel) ratios were investigated, in part. Physical and chemical properties of DME and gas oil are shown to lead to mutual solubility at any ratio. Blended fuels have a higher lubricity compared with pure’ DME and a better injection spray compared with pure gas oil.</div> <div class="htmlview paragraph">Blends including zero weight percent DME (neat gas oil operation), and nominal blend percentages of 2.5, 5, 10, 20, 40, 60, 80 and straight DME were evaluated in a single cylinder research test engine. Performance, emissions and other features of blended fuel operation yielded the following results:</div> <div class="htmlview paragraph">By taking relative advantages of DME and gas oil, the DME blended gas oil achieved satisfactory properties in lubricity and atomization, which contributed to improvements in leakage and spray characteristics.</div> <div class="htmlview paragraph">Engine performances were found to be comparable among the test fuels which contains a proportion of DME of up to about 10%.</div> <div class="htmlview paragraph">As much as 30% soot emission reductions could be achieved with about 10% DME blended fuel operation, however, no significant reductions in and unburned hydrocarbon emissions were observed.</div>

<div class="section abstract"><div class="htmlview paragraph">In recent years the 2-wheelers engines companies have been focused on increasing the overall engine efficiency, that can be achieved amongst other by engine down-speeding, engine down-sizing and by reducing the frictions; however, to maintain or improve vehicle performance, it is necessary to provide a corresponding increase in specific power.</div><div class="htmlview paragraph">In accordance with these trends, the studied approaches and methodologies have been exploited, during the development of the new Piaggio small scooter engine.</div><div class="htmlview paragraph">In this work a multi-objective analysis has been applied to the valve train system design, in order to optimize the engine performance in terms of friction reduction, power curve and timing system response. Along with this optimization methodology, a robust design has been studied to make the peak cranking compression pressure insensitive to the engine starting device working. These calculation methodologies have been followed using commercial software as GT-SUITE® code and the modeFRONTIER® platform for the multi-objective optimization analysis.</div><div class="htmlview paragraph">The several configurations investigated have allowed to reach the desired trade-off between the appropriate and efficient valve train behavior and the engine performances.</div><div class="htmlview paragraph">The global engine friction reduction has been obtained thanks to low resisting cam torque profiles, a specific valve springs set and a new compression releaser device (during engine starting phase).</div><div class="htmlview paragraph">The results have been further validated by an experimental campaign carried out on the test bench for engine performance and on the specific cold test bench to evaluate friction losses.</div></div>

<div class="htmlview paragraph">During last four years the authors were involved in the simulation and investigation of combustion and ionization in the cylinder of gasoline and natural gas Spark Ignition (SI) engine. Two-zone model of combustion and chemical non-equilibrium ionization and results of the numerous numerical investigation were presented by the authors at SAE 2002 and SAE 2003 World Congresses. This model and numerical results provided an important insight into combustion products behavior and gave the chance to find correlation between chemical and thermal ionization of combustion products and SI engine performances.</div> <div class="htmlview paragraph">In order to provide better correspondence of the numerical data to the experimental results in the wide range of operational parameters for different geometry of engines a new three-zone model was developed and successfully tested. In comparison with previous one new model includes the additional third zone, which simulates the processes in the small volume of flame kernel inside the gap between spark plug electrodes.</div> <div class="htmlview paragraph">Following processes in the flame kernel are taken into account:</div> <div class="htmlview paragraph"> <ul class="list disc"> <li class="list-item"><div class="htmlview paragraph">detailed mechanism of chemical interaction including chemical and thermal ionization;</div> </li> <li class="list-item"><div class="htmlview paragraph">heat exchange between combustion products and electrodes;</div> </li> <li class="list-item"><div class="htmlview paragraph">mass exchange between third zone and combustion products in the cylinder.</div> </li> </ul> </div> <div class="htmlview paragraph">The comparison of numerical and experimental results showed more accurate correlation between measured and calculated values of pressure and ion current. The concentration of electrons in the gap between spark plug electrodes corresponds better to the experimental data for gasoline engines in comparison with two-zone model. Three-zone model became a new generation among the models for the investigation of in-cylinder combustion products ionization and simulation of operational and ecological performances of SI engine.</div>