GRAPHITE FAN BLADE DEVELOPMENT

<div class="section abstract"><div class="htmlview paragraph">The introduction of alternative fuels is crucial to limit greenhouse gases. CNG is regarded as one of the most promising clean fuels given its worldwide availability, its low price and its intrinsic properties (high knocking resistance, low carbon content...). One way to optimize dedicated natural gas engines is to improve the CNG slow burning velocity compared to gasoline fuel and allow lean burn combustion mode. Besides optimization of the combustion chamber design, hydrogen addition to CNG is a promising solution to boost the combustion thanks to its fast burning rate, its wide flammability limits and its low quenching gap.</div><div class="htmlview paragraph">This paper presents an investigation of different methane/hydrogen blends between 0% and 40 vol. % hydrogen ratio for three different combustion modes: stoichiometric, lean-burn and stoichiometric with EGR. The main objectives are to identify the complex mechanisms involved in the combustion process and to define the optimal hydrogen ratio for each combustion mode.</div><div class="htmlview paragraph">The study combines engine tests and 0D modeling. Tests were carried out on a spark-ignited single-cylinder engine adapted to CNG operation with 2 different compression ratios 9,5:1 and 11,5:1. Computations allow studying separately the different phenomena linked to the progressive addition of hydrogen in the fuel. Hence, using 0D modeling, the effects due only to the combustion speed evolution, as a function of hydrogen ratio in the fuel, were then quantified using experimental results as comparison basis.</div><div class="htmlview paragraph">The engine test results reveal that the impact of hydrogen is limited in stoichiometric conditions except for CO₂ savings. A ratio of 10 to 20 vol. % of hydrogen seems to be optimal to reach interesting HC emissions reduction without an excessive lowering of the operation range. The results are more encouraging for lean-burn operation as the lean limit of equivalence ratio is extended for more than 0,125 with 40 vol. % of hydrogen. NOx emissions and consumption were significantly reduced (-92% for NOx) while maintaining constant HC and CO emissions compared to methane operation. Hydrogen stabilizes and speeds up combustion especially in very diluted mixtures. Furthermore, hydrogen increases EGR tolerance for the same reasons as in lean-burn mode: in comparison, identical very-low NOx levels were reached with smaller consumption gains. Finally, the engine test results show that the highest tested ratio of hydrogen (up to 40%) in methane for very diluted mixtures with air or EGR drastically reduce NOx emissions without penalty on engine performances.</div><div class="htmlview paragraph">Computations prove that the evolution in terms of thermodynamic properties of the fuel is not the most important contribution to the evolution of combustion. The effect of hydrogen addition contributes mainly to increase the combustion speed. Moreover, lean burn operation results demonstrate that the increase of combustion speed due to hydrogen addition is enhanced. This can only be explained by the increase of thermo-diffusivity which has an opposite and larger effect than the slowdown of laminar flame velocity conventionally described in the literature.</div></div>

This experimental study presents the Lamb wave based baseline-free diagnostics of damage in a carbon-fiber composite fan blade using the Modified Time Reversal Method (MTRM). A fan blade with delamination was selected as the test specimen and two piezoelectric transducers (PZT) were surface bonded using epoxy adhesive. The system (fan blade and transducers) was then waveform-tuned from which 5.5 cycle tone burst was selected as the optimum excitation waveform. The system was then mode-tuned in order to determine the optimum excitation center frequency. The 55 kHz, 5.5 cycle tone burst was used to generate fundamental asymmetric Lamb waves with high signal-to-noise ratio and low dispersion. Damage Index (DI) values for the fan blade was calculated at equidistant points on a line using both PZTs. Results show that magnitudes of the DI values have strong correlation with the severity of damage present in the fan blade. The procedure followed in this experimental study is directly applicable to the Non Destructive Evaluation (NDE) conducted on composite fan blades. Additionally, this method can be extended to develop a real-time structural health monitoring system for composite fan blades which employs embedded PZTs for actuating and sensing waves.

<div class="htmlview paragraph">This paper reviews ASTM's work in developing the new API CH-4 diesel engine oil category for 1998. It focuses in particular on three new engine tests - Cummins M-11, Mack T-9, and Caterpillar 1P - which are juxtaposed on existing engine and bench tests in the API CG-4/CF-4 categories. These new tests ensure increased engine durability, while operating at high temperatures and high levels of soot in the crankcase. The high soot levelsMP expected in 1998 emission-controlled engines are a result of retarded fuel injection timing used to lower NOx, combined with high top-ring piston locations used to minimize particulate.</div> <div class="htmlview paragraph">API CH-4 is the most robust API diesel engine oil category ever developed. It improves the quality of diesel engine oils for both existing and new engines, using both low and normal fuel sulfur levels. In addition, it will allow a more flexible approach to oil drain intervals, in accordance with the recommendations of the individual engine manufacturers.</div>

<div class="htmlview paragraph">The use of naphthenic base stocks in the formulation of engine oils has always been restricted due to certain physico-chemical properties (i.e. low oxidation stability, high volatility, great variation of the viscosity with the temperature) as well as the limited availability of this type of base oil in many parts of the world.</div> <div class="htmlview paragraph">However, modern additive technologies have permitted the formulation of high quality engine lubricants that incorporate a considerable proportion of naphthenic base stocks.</div> <div class="htmlview paragraph">This paper summarizes the experimental results followed in the development of a crank-case engine oil formulation SAE 40. API SF/CC with maximun usage of a naphthenic base stock MVIN-170 combined with HVI stocks and conventional additive technologies. The physico-chemical characterization of the MVIN-170 base stock, a conventional processed naphthenic oil that Maraven (affiliate of PDVSA) commercializes from Isla Refinery of Curasao, is presented and compared with other naphthenic oils coming from other crude sources or processes and with paraffinic base stocks of equivalent viscosity. Further, it describes the different approaches in terms of base stocks balance and additives treat rates, used in the development of the final oil formulation showing in each case the corresponding engine test results.</div> <div class="htmlview paragraph">These types of formulations appear as an excellent alternative in terms of cost/performance for gasoline and diesel engines operating in mild weather regions of the world.</div>

<div class="section abstract"><div class="htmlview paragraph">Combustion simulations and single cylinder engine tests show a clear potential when coupling the Variable Compression Ratio (VCR) engine with the Variable Valve Actuation (VVA) technologies.</div><div class="htmlview paragraph">Simulations demonstrate the thermodynamic benefit from increasing the geometric Compression Ratio (CR>18:1) in combination with VVA compared to VVT strategies, thanks to the use of Atkinson / Miller Cycles. 3D combustion simulations of high compression ratio combustion chamber geometries used with Early or Late Intake Valve Closing strategies have been carried out with IFP-C3D™. They show an indicated efficiency increase up to 12 or 13% between compression ratio 10:1 and 18-20:1 at low loads (BMEP < 8 bar).</div><div class="htmlview paragraph">Single cylinder engine tests have been performed with specific combustion chambers up to CR 23:1 and have confirmed the simulation results.</div><div class="htmlview paragraph">0D GT-POWER™ simulations have been correlated to the engine tests and used to extrapolate them to a 3 cylinders 1.1L TGDI VCR-VVA engine, for both EIVC and LIVC intake valve lift strategies.</div><div class="htmlview paragraph">Finally, simulations and tests show correlated thermodynamic benefits of the association of VCR and VVA, improving fuel consumption on driving cycles between 8 and 11% compared to a 10.5:1 fixed compression ratio engine equipped with 2 VVT. Combining the VCR and VVA optimizes each potential far more than when separated (alone). Furthermore, the fuel consumption benefit is robust through driving cycles and downsizing level. </div></div>

<div class="htmlview paragraph">The present paper focuses on a system and an appropriate controller concept for an advanced air management system of a turbocharged passenger car diesel engine. The proposed air management system consists of a VTG turbocharger, two separate EGR loops, a non-cooled high-pressure EGR and a cooled low-pressure EGR loop. In the low pressure EGR loop, the exhaust gas leaving the particulate filter is mixed with fresh air just in front of the compressor inlet.</div> <div class="htmlview paragraph">The first step consisted of developing a sensor and actuator concept. Prior to conducting engine tests on this system, GT power simulations were performed. Additionally, a MATLAB/Simulink model was created to design a model-based predictive controller. This model is mainly founded on physical equations, allowing for easy adaptation to various systems.</div> <div class="htmlview paragraph">At the beginning of the engine test stage, stationary measurements were conducted to examine the influence of variations of the EGR rate, boost pressure, fresh air mass, etc. These tests were carried out in an open loop without an integrated controller for the air management system. The results were used to optimize the Simulink simulation model.</div> <div class="htmlview paragraph">As to the controller concept, a model-based predictive approach is presented which uses a simplified simulation model of the complete air path for the prediction.</div> <div class="htmlview paragraph">Furthermore, the system design on the dynamometer and the interaction of the individual steps are described. Simulation results of the new controller type and first results of the controller on the dynamometer are presented, as well.</div> <div class="htmlview paragraph">Due to modifications of the state-of-the-art high-pressure system arising from the integration of a low-pressure EGR line, additional measures need to be taken to protect the components in the inlet air path from harmful impact resulting from corrosion and particulates.</div>

<div class="htmlview paragraph">Optical studies of combusting diesel sprays were done on three different alternative liquid fuels and compared to Swedish environmental class 1 diesel fuel (MK1). The alternative fuels were Rapeseed Oil Methyl Ester (RME), Palm Oil Methyl Ester (PME) and Fischer-Tropsch (FT) fuel.</div> <div class="htmlview paragraph">The studies were carried out in the Chalmers High Pressure High Temperature spray rig under conditions similar to those prevailing in a direct-injected diesel engine prior to injection. High speed shadowgraphs were acquired to measure the penetration of the continuous liquid phase, droplets and ligaments, and vapor penetration. Flame temperatures and relative soot concentrations were measured by emission based, line-of-sight, optical methods. A comparison between previous engine tests and spray rig experiments was conducted in order to provide a deeper explanation of the combustion phenomena in the engine tests.</div> <div class="htmlview paragraph">Results pertaining to spray behavior show that high viscosity fuels have wider spray cone angles, smaller discharge coefficients (Cd) and shorter vapor penetration than low viscosity fuels. Continuous liquid phase penetration is related to differences in surface tension, viscosity and density; while the penetration of droplets and ligaments is related to volatility, their penetration is short for highly volatile fuels and long for low-volatility fuels.</div> <div class="htmlview paragraph">Engine tests show that particle matter (PM) emissions are generally lower when these alternative fuels are used, but the use of RME leads to increased NO<sub>x</sub> emissions correlating with elevated flame temperatures.</div>

<div class="htmlview paragraph">A European test procedure for evaluating engine deposits, using the Mercedes Benz M111 bench engine, has already been approved for inlet valve deposits (IVD) and is under development for combustion chamber deposits (CCD) by the Co-ordinating European Council (CEC). This paper describes CCD effects on emissions using a slightly modified version of this engine test procedure and compares it with CCD/emissions data from road vehicles.</div> <div class="htmlview paragraph">The engine used was a modern four valve, four cylinder, 2.0 litre passenger car unit and the bench test procedure used extended the operating time from the specified 60 hours to 180 hours. The road vehicle trial used two Mercedes Benz C200 passenger cars fitted with the M111 engine and two Ford Mondeo 2.0 litre passenger cars. Data was collected up to 11200km, approximately equivalent to 180 hours operation of the bench engine.</div> <div class="htmlview paragraph">For both bench and road vehicles, CCD was monitored by measuring CCD thickness on the piston crown through the spark plug hole, together with measurements of the overall changes in CCD and IVD mass on completion of the test. Engine out emissions were measured continuously throughout each engine test and periodically during the road trials.</div> <div class="htmlview paragraph">The results have established how CCD, NOx and fuel economy vary with time/mileage for both the M111 bench engine and for two models of road vehicles. Trends between CCD growth and the changes in NOx and fuel consumption were in broad agreement for both the engine tests and the road trials. These results increase the confidence in the M111 test as an effective means of not only measuring CCDs but also linking deposits to associated NOx emission changes.</div>

<div class="htmlview paragraph">The current SI engine designs submit the engine to operating conditions that require an improved performance of its components. The increase of the engine speed is a trend that generates a significant change in the engine components design approach.</div> <div class="htmlview paragraph">During validation tests, some engines have presented blow-by spikes at high speed and low load operating conditions. The reason is an abnormal ring package motion due to the influence of the high inertia and small gas pressure loads.</div> <div class="htmlview paragraph">This work presents a numerical simulation of a SI engine considering high speed and no load operating conditions, which showed blow-by spikes during engine tests. The numerical simulation tends to reproduce the blow-by spikes and identify the involved phenomena.</div> <div class="htmlview paragraph">Based on the numerical simulation, other engines were analyzed and some guidelines for the piston and the piston rings were developed in order to minimize the blow-by spikes at the mentioned operating condition. Some engine tests have been done to support the guidelines.</div>

<div class="section abstract"><div class="htmlview paragraph">The use of piezoelectric cylinder pressure sensors is very popular during engine testing, but cylinder pressure information is becoming mandatory also in several on-board applications, where Low Temperature Combustion (LTC) approaches require a feedback control of combustion, due to poor combustion stability and the risk of knock or misfire.</div><div class="htmlview paragraph">Several manufacturers showed the capability to develop solutions for cylinder pressure sensing in on-board automotive and aeronautical applications, and some of them have been patented. The most straight-forward approach seems the application of a piezo-electric washer as a replacement of the original part equipping the spark plug; the injector could also be used to transfer the cylinder pressure information to the piezoelectric quartz, in diesel or Gasoline Direct Injections (GDI) engines.</div><div class="htmlview paragraph">The paper describes the features of signals acquired using piezoelectric washers, discussing possible applications, highlighting the factors which impact the sensors accuracy, and proposing algorithms to compensate potential errors in the evaluation of combustion metrics. The sensors have been first tested on a press, then in two different gasoline engines: a naturally aspirated V12 and a turbocharged 2 cylinders with Variable Valve Lift system (VVL). Signals have been compared to those obtained with lab-grade cylinder pressure sensors, with particular attention to peak pressure, combustion phase and knock intensity.</div><div class="htmlview paragraph">The main issue affecting the accuracy of cylinder pressure measurement using the piezoelectric spark plug washer is the effect of temperature variations both on the force transmitted by the thread to the washer and piezoelectricity properties.</div></div>

<div class="section abstract"><div class="htmlview paragraph">The American Petroleum Institute’s (API) Single Technology Matrix (STM) is a data-based, Virtual Testing process and protocol (utilizes test data, characteristics and features of base stocks and blends coupled with statistical methods and analysis) used to predict the performance capability of a specific engine oil additive technology in a single specified base oil, in a given engine test. The concept was first introduced in 2002, codified and implemented by API in 2007, and updated in 2022. The previously published advantages of STM in the proof-of-performance of engine oils, remain relevant.</div><div class="htmlview paragraph">These advantages include a data space focused on interpolation, documented statistical analysis protocol, limitation to a specific formulation, flexibility in understanding complicated, interactive, or non-linear technology and base oil relationships, and timeliness.</div><div class="htmlview paragraph">There have been numerous changes to, and in, the engine oil industry since the introduction of STM in 2007. These include advances in base stock refining practices, improvement in additive technology, lower viscosity oils, supply chain issues due to local and global disruptive events, test capacity issues due to stalled industry growth and increased regulatory practices. The enhancement of the STM process for both 2022 and beyond is warranted and justified in response to these changes.</div><div class="htmlview paragraph">This paper serves as an educational tool, not an instructional manual, on the STM concept to enhance understanding and perspective of the current concept not provided elsewhere, as well as the improvement of the process to address the evolving performance testing and base oil characterization needs of the future. It is an important first step in the necessary continuous dialogue on the protocol and the future data needs to support the protocol.</div></div>

<div class="htmlview paragraph">There is a strong request for heavy-duty gas engines in the Nordic countries for environmental reasons. Therefore, several research projects are going on. This paper describes two of them: a Finnish Sisu truck and a MAN bus, both operating in the city of Espoo, the hometown of the Technical Research Centre.</div> <div class="htmlview paragraph">The truck is equipped with a 7.4 litre Finnish Valmet 612 engine. The development work has included engine tests and tests with a vehicle in laboratory conditions. A 3,3 litre 3-cylinder engine was used for the engine tests. The engine runs on stoichiometric mixture, and has a three-way catalyst based on metal substrate. The engine was run on both methane (compr. ratio 12:1) and propane (compr. ratio 10:1).</div> <div class="htmlview paragraph">Emissions were extremely low with both fuels. In the European 13-mode test 0.4 g CO, 0.1 g HC and 0.1 g NO<sub>x</sub> per kWh were achieved. Peak thermal efficiency was 35 % for both fuels. Maximum mean effective pressure (BMEP) for a naturally aspirated engine is 9 - 9,5 bar. Turbocharging was tested with propane, and a knock limited BMEP of 12.5 bar was reached.</div> <div class="htmlview paragraph">The truck has been operating on propane since the beginning of 1990. The naturally aspirated 7.4 litre engine gives a maximum power output of 130 kW. Results from tests carried out, both on the road and in laboratory conditions, are given.</div> <div class="htmlview paragraph">The MAN bus is also running on propane and uses stoichiometric air-fuel mixture. The technology is similar to the one used in the city of Vienna. The displacement of the engine is 12 litres, and the maximum power output is 177 kW. The bus has been operating since the beginning of April 1991. It is covered with an extensive follow-up program including exhaust emission measurements. This paper describes these procedures and presents results of the first tests.</div>

<div class="section abstract"><div class="htmlview paragraph">This paper presents the results of a study on reasons for the occurrence of pre-ignition in highly supercharged spark ignition engines. During the study, the phenomena to be taken into account were foremost structured into a decision tree according to their physical working principles. Using this decision tree all conceivable single mechanisms to be considered as reasons for pre-ignition could be derived. In order to judge each of them with respect to their ability to promote pre-ignition in a test engine, experimental investigations as well as numerical simulations were carried out.</div><div class="htmlview paragraph">The interdependence between engine operating conditions and pre-ignition frequency was examined experimentally by varying specific parameters. Additionally, optical measurements using an UV sensitive high-speed camera system were performed to obtain information about the spatial distribution of pre-ignition origins and their progress.</div><div class="htmlview paragraph">The numerical simulations included the analysis of the general auto-ignition behavior of air/fuel mixtures depending on the thermodynamic conditions, mixture composition and other factors by taking into account detailed reaction kinetics. Furthermore, 3D CFD simulations were conducted in order to determine the predominant conditions within the combustion chamber.</div><div class="htmlview paragraph">By combining the results of the experimental and numerical investigations, many of the identified mechanisms could be ruled out. Others were classified to be very improbable. The release of lubricant oil droplets from the cylinder liner turned out to be the most probable explanation for the occurrence of pre-ignition. As a main factor influencing the amount of droplets released and hence the pre-ignition frequency, oil dilution caused by spray impingement due to the lateral injector position was identified.</div></div>

<div class="section abstract"><div class="htmlview paragraph">This study presents estimates for measurement uncertainties for a Homogenous Charge Compression Ignition (HCCI)/Low-Temperature Gasoline Combustion (LTGC) engine testing facility. A previously presented framework for quantifying those uncertainties developed uncertainty estimates based on the transducers manufacturers’ published tolerances. The present work utilizes the framework with improved uncertainty estimates in order to more accurately represent the actual uncertainties of the data acquired in the HCCI/LTGC laboratory, which ultimately results in a reduction in the uncertainty from 30 to less than 1 kPa during the intake and exhaust strokes. Details of laboratory calibration techniques and commissioning runs are used to constrain the sensitivities of the transducers relative to manufacturer supplied values. The uncertainty framework is also extended to consider additional sources of uncertainty, including non-ideal engine volume history due to kinematic effects on the effective connecting rod length. Finally, the uncertainty propagation chain is analyzed to determine primary uncertainty sources, and mitigations are discussed.</div></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>