Achieving stable combustion without misfire and knocking is challenging in premixed charge compression ignition (PCCI) especially in small bore, air cooled diesel engines owing to lower power output and inefficient cooling system. In the present study, a single cylinder, air cooled diesel engine used for agricultural water pumping applications is modified to run in PCCI by replacing an existing mechanical fuel injection system with a flexible common rail direct injection system. An advanced start of fuel injection (SOI) and exhaust gas recirculation (EGR) are required to achieve PCCI in the test engine. Parametric investigations on SOI, EGR and fuel injection pressure are carried out to identify optimum parameters for achieving maximum brake thermal efficiency. An SOI sweep of 12 to 50 deg. CA bTDC is done and for each SOI, EGR is varied from 0 to 50% to identify maximum efficiency points. It was found that EGR helps in extending the load range from 20 to 40% of rated load.
The fuel economy of recent small size DI diesel engines has become more and more efficient. However, heat loss is still one of the major factors contributing to a substantial amount of energy loss in engines. In order to a full understanding of the heat loss mechanism from combustion gas to cylinder wall, the effect of hole size and rail pressure under similar injection rate conditions on transient heat flux to the wall were investigated. Using a constant volume vessel with a fixed impingement wall, the study measured the surface heat flux of the wall at the locations of spray flame impingement using three thin-film thermocouple heat-flux sensors. The results showed that the characteristic of local heat flux and soot distribution was almost similar by controlling similar injection rate except for the small nozzle hole size with increasing injection pressure.
Two-stroke (2S) engines still play a key role in the global internal combustion engine (ICE) market when high power density, low production costs, and limited size and weight are required. However, they suffer from low efficiency and high levels of pollutant emissions, both linked to the short circuit of fuel and lubricating oil. Low- and high-pressure direct injection systems have proved to be effective in the reduction of fuel short circuiting, thus decreasing unburnt hydrocarbons and improving engine efficiency. However, the narrow time window available for fuel to be injected and homogenized with air, limited to few crank-angles, leads to insufficiently homogenized fuel-air mixtures and, as a consequence, to incomplete combustions. The use of prechambers can be a well-suited solution to avoid these issues.
Lean burn gasoline engines can achieve noteworthy fuel consumption and power output. However, when the mixture becomes lean, the ignition delay increases, and the flame propagation speed becomes slow, which lead to increase the combustion fluctuation. The glow plug is usually used to solve the cold start problem in diesel engines, where the compression temperature might not be high enough to ensure the proper ignition of the injected fuel, resulting in instability combustion and increased exhaust emissions. Based on this point, the present study intends to install a glow plug to the sub-chamber. Experiments were conducted on a modified single cylinder four-stroke CI engine (YANMAR TF120V) to operate as SI engine with a higher compression ratio compared to the conventional SI engines, 15.1:1. The engine is operated at a constant speed of 1000 rpm for different equivalence ratios with different voltage of glow plug which creates the temperature variation inside the sub-chamber.
In the present work, a relative comparison of addition of water to diesel through emulsion and fumigation methods is explored for reducing oxides of nitrogen (NOx) and smoke emissions in a production small bore diesel engine. The water to diesel ratio was kept the same in both the methods at a lower concentration of 3% by mass to avoid any adverse effects on the engine system components. The experiments were conducted at a rated engine speed of 1500 rpm under varying load conditions. A stable water-diesel emulsion was prepared using a combination of equal proportions (1:1 by volume) of Span 80 and Tween 80. The mixture of Span 80 in diesel and Tween 80 in water was homogenized using an IKA Ultra Turrax homogenizer with tip stator diameter 18mm at 5000 rpm for 2 minutes. The water-in-diesel emulsions thus formulated were kinetically stable and appeared translucent. No phase separation was observed on storage for approximately 105 days.
Amid the increasing demand for higher efficiency in combustion driven handheld tools, the recent developments in electric machine technology together with the already existing benefits of small combustion engines for these applications favor the investigation of potential advantages in hybrid powertrain tools. This concept-design study aims to use a fully parametric, system-level simulation model with exchangeable blocks, created with a power-loss approach in Matlab and Simulink, in order to examine the potential of different hybrid configurations for different tool load cycles. After the model introduction, the results of numerous simulations for 36 to 100 cc engine displacement will be presented and compared in terms of overall system efficiency and overall powertrain size. The different optimum hybrid configurations can show a reduction of up to 30 % in system’s brake specific fuel consumption compared to the baseline combustion engine driven model.
The combustion and emission formation in the advanced low temperature combustion (LTC) engine strategies are highly sensitive to fuel molecular composition and properties. Ignition timing in LTC is primarily controlled by fuel chemical kinetics and thus, tailoring of fuel properties is required to address its limitations in-terms of lack of control on ignition timing and narrow operating load range. Utilizing fuel blends and additives such as nanoparticles are one of the promising approaches to achieve targeted fuel property. An improved understanding of fundamental processes including fuel evaporation is required owing to its role in fuel-air mixing and thereby emission formation in LTC. In the present work, evaporation characteristics of blends of commercial fuels, viz. gasoline, diesel and alternative fuels, viz. ethanol and butanol are investigated. Further, graphene based nanoadditives at 0.05 wt % in gasoline, diesel and butanol are also investigated.
The growing EV market and tougher EURO VI regulations require to further reduce the presence of diesel engines. However, diesel engines still have the advantages in high performance and high thermal efficiency, while It produces NOx and PM. Therefore, diesel engines should recognize the need for change. It is important to improve and practicalize innovative combustion technologies that can improve fuel efficiency without losing power in consideration of emission regulations. In that point view, the new combustion technology have been studied such as Premixed Charge Compression Ignition(PCCI) . This combustion technology can reduce both NOx and PM emissions through longer mixing time and Low Temperature Combustion(LTC) by applying advanced injection than conventional diesel combustion, In this study, numerical analysis for PCCI engine is performed to optimize injection angles that can reduce wall wetting, increase fuel efficiency and reduce emissions.
Measuring brake emission is still a challenging non-standardized task. Extensive research is ongoing. Updates of work in progress are presented at SAE Brake Colloquium and PMP meetings. However, open items include how to achieve lower background concentration and how to design the brake enclosure. A low background concentration is essential as brake events are short and some emit in the range of reported background levels. Hence these emissions are difficult to distinguished from the background level. Even more critical, a high background concentration can result in a wrong particle number emissions value, either overestimated, background counted as emissions, or underestimated, background level subtracted, and low emission events no longer detected and counted. However, reducing the background level to less than 100 #/cm³ appeared to be quite challenging.
Raising demands towards lightweight design paired with a loss of originally predominant engine noise pose significant challenges for NVH engineers in the automotive industry. From an aeroacoustic point of view, low frequency buffeting ranks among the most frequently encountered issues. The phenomenon typically arises due to structural transmission of aerodynamic wall pressure fluctuations and/or, as indicated in this work, through rear vent excitation. A possible workflow to simulate structure-excited buffeting contains a strongly coupled vibro-acoustic model for structure and interior cavity excited by a spatial pressure distribution obtained from a CFD simulation. In the case of rear vent buffeting no validated workflow has been published yet. While approaches have been made to simulate the problem for a real-car geometry such attempts suffer from tremendous computation costs, meshing effort and lack of flexibility.
With battery electric vehicles (BEV), due to the absence of the combustion process, the rolling noise comes even more into play. The BEV technology also leads to different concepts of how to mount the electric engine in the car. Commonly, also applied with the Audi e-tron, the rear engine is mounted on a subframe, which again is connected to the body structure. This concept leads to a better insulation in the high frequency range, yet it bears some problems in designing the mounts for ride comfort (up to 20Hz) or body boom (up to 70Hz). Commonly engine mounts are laid-out based on driving comfort (up to 20Hz). The current paper presents a new method to find an optimal mount design (concerning the stiffness) in order to reduce the dynamic chassis forces which are transferred to the body up to 100Hz. This directly comes along with a reduction of the sound pressure level for the ‘body boom’ phenomena.
This work focuses on the effects of cooled Low Pressure EGR and Water Injection observed by conducting experimental tests consisting mainly of Spark Advance sweeps at different cooled LP-EGR and WI rates. The implications on combustion and main engine performance indexes are then analysed and modelled with a control-oriented approach, showing that combustion duration and phase and exhaust gas temperature are the main affected parameters. Results show that cooled LP-EGR and WI have similar effects, being the associated combustion speed decrease the main cause of exhaust gas temperature reduction. Experimental data is used to identify control-oriented polynomial models able to capture the effects of LP-EGR and WI on both these aspects. The limitations of LP-EGR are also explored, identifying maximum compressor volumetric flow and combustion stability as the main ones.
Diesel engines with their embedded control systems are becoming more and more complex as the emission regulations tighten, especially concerning NOx pollutants. The combustion and emission formation processes in diesel engines are closely correlated to the intake manifold O2 concentration. Consequently, the performance of the main engine controllers can be improved significantly, if a model-based or sensor-based estimation of the intake O2 concentration is available in the ECU. The paper addresses the modeling of the intake manifold O2 concentration in a turbocharged diesel engine. Dynamic models, compared to generally employed steady state maps, capture the dynamic effects occurring over transients. It is right in the transient that the major deviations from the stationary maps are found. The dynamic model will positively affect the control system making it more effective.
The numerical reconstruction of the liquid jet generated by a multi-hole injector, operating in flash-boiling conditions, has been developed by means of an Eulerian- Lagrangian CFD code and validated thanks to experimental data collected with schlieren and Mie scattering imaging techniques. The model has been tested with different injection parameters in order to recreate various possible engine thermodynamic conditions. The work carried out is framed in the growing interest present around the gasoline direct-injection systems (GDI). Such technology has been recognized as an effective way to achieve better engine performance and reduced pollutant emissions. High-pressure injectors operating in flashing conditions are demonstrating many advantages in the applications for GDI engines providing a better fuel atomization, a better mixing with the air, a consequent more efficient combustion and, finally, reduced tailpipe emissions.
The growing need for a sustainable worldwide mobility is leading towards a paradigm shift in the automotive industry. The increasingly restrictive regulations on vehicle emissions are indeed driving all of the world-leading road vehicles manufacturers to redesign the concept of transportation by developing new propulsion solutions. To this aim, a gradual electrification strategy is being adopted, and several hybrid electric solutions, such as extended-range electric vehicles with reciprocating engines or fuel cells, already represent a valid alternative to conventional vehicles powered by fossil fuels. Despite their appealing features, these hybrid propulsion systems present some drawbacks, mainly related to their complex architecture, causing high overall dimensions, weight and costs, which pose some limitation in their use for small-size vehicles.
Pollutant emission of vehicle cars is nowadays a fundamental aspect to take into account. In the last decays, the company have been forced to study new solutions, such as alternative fuel and learn burn mixture strategy, to reduce the vehicle’s pollutants below the limits imposed by emission regulations. Pre-chamber ignition system presents potential reductions in emission levels and fuel consumption, operating with lean burn mixtures and alternative fuels. The aim of this work is to study the evolution of the plasma jets in a different in-cylinder conditions. The activity was carried out in a research optical small spark ignition (SI) engine equipped alternatively with standard ignition system and per-chamber. The engine runs at 2000 rpm at wide open throttle (WOT) in standard ignition condition and slightly turbocharged in prechamber condition in order to overcame the decrease of compression ratio. In this activity methane and gasoline were used.
Mechanical friction and heat transfer in internal combustion engines are two highly researched topics, due to their importance on the mechanical and thermal efficiencies of the engine. Despite the research efforts that were done throughout the years on both these subjects, engine modeling is still somewhat limited by the use of models which do not fully represent the phenomena happening in the engine. Developing new models require experimental data which is accurate, repeatable and which covers wide range of operation. In 2018-01-0121, the conventional pressurised motored method was investigated, and compared with other friction determination methods. The pressurised motored method proved to offer a good intermediate between the motored tests, which offer good repeatability, and the fired tests which provide the real operating conditions, but lacks repeatability and accuracy.