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Robust engine operation with long maintenance intervals and low emissions is the key to meeting future engine requirements. At the same time, engines should be environmentally friendly, resource-friendly, and cost-effective to produce and operate. To meet these market requirements, a central component in engine development is the ignition system and in particular the spark plug. To increase the maintenance intervals of internal combustion engines, it is necessary to increase spark plug lifetime by reducing spark plug wear. The electrode materials used to date are often expensive and rare, and their mining is not without controversy. Successful use of alternative spark plug electrode materials which are available in large quantities, inexpensive, and more resistant to wear than existing materials with similar ignition behavior would advance engine development so it can meet further economic and environmental requirements. To this end, ceramic spark plug electrodes were investigated to determine their spark and ignition behavior as well as their wear. These materials seem to be an interesting alternative to existing spark plug electrode materials. This paper presents a spark plug with ceramic spark plug electrodes that achieves conditions similar to those of standard spark plugs in terms of secondary voltage trace and ignition behavior. Furthermore, it introduces a sophisticated method for scientific, cost-effective, and application-oriented development. Finally, it provides a promising outlook for the ignition behavior and combustion performance of engines with this spark plug.

The research and development of combustion engines will face multiple challenges during the next years. Increasing reliability while further reducing emissions and life cycle costs are just a few of them. The reduction of the lubrication oil consumption (LOC) addresses all the aforementioned challenges. Reducing the oil consumption of an engine, reduces emissions like particle emissions, hydrocarbon emissions and combustion anomalies. However, the biggest incitement for optimizing the oil consumption would be to lower the life cycle cost through extending the durability of the exhaust gas aftertreatment system, as contaminants coming from the oil are considered to lead to poisoning of catalytic materials. In addition, it is also important to take the cost of the lubrication oil itself into account as well. Thus, especially for manufacturers of large stationary gas engines, reducing – or rather, optimizing – the lube oil consumption is becoming more and more of a focus. However, a further reduction of the LOC causes state-of-the-art measurement methods to reach their limitations regarding resolution and lower detection limit (LDL). Hence, new methods need to be developed. Most currently available systems are based on the tracer technology, where a naturally abundant or synthetically added substance of the oil is traced down in the exhaust gas. By quantifying the amount of tracer in the exhaust gas, the LOC can be calculated. The newly developed and patented (Rossegger and Engelmayer, 2018) [1] method presented in this article is based on the use of the stable hydrogen isotope deuterium (2H) as a tracer. It is added to the oil by conducting a hydrogen/deuterium (1H/2H) exchange process with synthetic oil, which is then blended into the oil. When operating the engine, the deuterium can be detected in the exhaust gas water vapor using an isotopic water analyzer based on the cavity ring-down spectroscopy (CRDS). The present article will first focus on the synthesis of the tracer, then on the design of a prototype and finally present measurement results collected on a passenger car engine.

Lube oil emission is thought to have a negative influence on hydrocarbon and particle emissions, autoignition and the life-cycle cost of internal combustion engines. Thus, one of the major goals of combustion engine research and development is to optimize lube oil consumption, for example by optimizing the tribological behavior of the piston group (interaction between piston rings and cylinder liner). This requires the application of a fast and accurate lube oil consumption measurement method. Methods such as gravimetric and volumetric measurement are outdated for R&D applications because of measurement time, absolute accuracy as well as repeatability, however some OEMs are still applying this method. At present, the use of tracer methods for measuring lube oil consumption is considered the most promising in terms of decreasing measurement time and increasing accuracy. For example, sulfur as a tracer is one of the most established methods for measuring lube oil consumption, but previous publications have revealed downsides and future challenges of its use. This publication, however, highlights the challenges of using the stable hydrogen isotope deuterium as a tracer which are still to overcome, in order to become a viable and reliable method for measuring lube oil consumption on internal combustion engines. In the introduction, a novel concept of measuring lube oil consumption with deuterated engine oil and the test bench setup are explained. Following laboratory experiments, test bench runs on a heavy-duty diesel engine and long-term studies on a field engine, three major challenges facing the new approach are identified and potential solutions are proposed. First, the long-term stability of the tracer in the lube oil and potential changes in the physical and chemical properties of the oil due to deuteration are discussed in light of the results of tests on a field engine that uses deuterated engine oil. Second, the hydrogen-deuterium exchange process to mark the oil with the tracer is examined and potential approaches for reducing cost and duration are highlighted. The universal applicability of the deuteration process to several base oil groups is also explained. Finally, the detection of deuterium in the gas of the engine exhaust and potential cross-sensitivities to trace gases as well as other crucial limitations of the detector in analyzing engine exhaust are addressed. The summary presents the requirements for converting the experiments with a deuterium tracer into a reliable method for lube oil consumption measurement providing crucial properties such as high accuracy, short measurement time, effort and ease of use.

Measures exist to adjust tailpipe NOx emissions to assigned values, for example cooled exhaust gas recirculation (EGR) or a SCR catalyst in conjunction with urea. The situation is quite different with soot when use of a trap is not feasible for reasons of cost, space requirements and maintenance. Due to the highly complex soot formation and oxidation process, soot emissions can’t be targeted as easily as NOX. So how can soot be kept within the limits? In principle, soot can be controlled by allocating sufficient oxygen and establishing good mixing conditions with vaporized fuel. The most effective measures target the injection system, e.g. increasing injection pressure, applying multiple injections, optimizing nozzle geometry. To investigate the impact of very high injection pressure on soot, an advanced injection system with rail pressure capability up to 3000 bar and a Bosch injector was installed at the Large Engines Competence Center (LEC) in Graz. Full load and part load operating points at constant speed and in accordance with the propeller law were investigated at the test bed to quantify the impact of high injection pressure on soot emissions. Test runs were conducted with both SCR and EGR while varying injection timing and air-fuel ratios. Use of a statistical method, Design of Experiments (DOE), helped reduce the number of tests. Optical investigations of the spray and combustion were conducted. The goal was to obtain soot concentration history traces with the two color method in order to better understand how soot originates and to be able to calibrate 3D CFD FIRE spray models for use with injection pressures of up to 3000 bar. Very low soot emissions can be achieved using high pressure injection, even when EGR is applied. DOE results provide a clear picture of the relationships between the parameters and can be used to optimize set values for the whole speed and load range. A reliable spray break up model can be used in further 3D CFD simulation to investigate how to reduce soot emissions.

The development of low-emission combustion concepts for large Diesel engines requires a specially adapted methodology. In all phases of the development process, it is essential that appropriate tools are used so that an optimized solution can be found within a short time. This paper will describe the methodology used for developing combustion concepts for large Diesel engines. In general, the development of a combustion concept for Diesel engines comprises the definition of the system (e.g. combustion chamber geometry, injection system, EGR system and charging system) and the calibration of engine parameters (e.g. injection parameters, EGR rate, charge pressure, excess air ratio and valve timing) for an application and its emission scenario. In the present case, the main objective was to develop concepts for applications to comply with emissions standards according to EU Stage III B and US EPA Tier 4. To this end, the LEC has developed the LDM method (LEC Development Methodology). This method is based on the intensive interaction of simulation with experimental investigations on single-cylinder research engines. As part of this development methodology, 3D CFD simulation as well as 0D and 1D engine cycle calculation are employed. Another approach used to handle the complexity of the systems is Design of Experiments (DoE) for simulation and experimental work. While 3D CFD simulation is used to optimize the details of the combustion and pollutant formation processes in the combustion chamber, 0D and 1D engine cycle simulation is applied to select the concepts and to pre-optimize important engine parameters. One great advantage of 0D and 1D models is their short calculation time, which allows the investigation of a great amount of variations in parameters. In order to apply the methodology, it must be guaranteed that the results from tests on the single-cylinder engine (SCE) can be transferred to the multi-cylinder engine (MCE). Therefore, it is necessary that the boundary conditions of the SCE are comparable to those of the MCE. Not only the same thermal boundary conditions but also the same conditions at the beginning of the high-pressure cycle (charge composition, pressure and temperature) must be maintained. The SCE measurement results that are generated serve to verify and calibrate the simulation models and deliver the necessary boundary conditions for further simulations. All in all, the paper comprises an evaluation of the different simulation models used and the applied development methodology in order to optimize fuel consumption and to reduce the emissions of large Diesel engines.Copyright © 2011 by ASME

The paper compares engine performance and economics for two combustion systems which were designed, optimized and tested on the same gas engine featuring approximately 5 liter per cylinder displacement and 1500 rpm engine speed. The traditional open-chamber spark-ignited combustion system (SIOC) was in competition with the pre-chamber micro pilot (PCMP) combustion system which involved gas combustion ignited by a very low diesel fuel quantity injected into the prechamber. The paper gives an insight into the two different combustion systems by showing and comparatively analyzing measurement results. The impact of both systems on combustion specifics, turbocharging and ignition systems are discussed. Combustion and thermodynamics benefits of the PCMP system are correlated to the additional development effort and systems required as well as to engine cost. Finally a strategic conclusion is drawn on the combustion system to be chosen in view of future engine performance and emission requirements and with respect to the economics of a gas engine of this size.Copyright © 2005 by ASME