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.
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.
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.
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.
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.
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.
Particles emitted from internal combustion engines have adverse health effects. The severity varies based on the particle size as they deposit at different parts in the respiratory system. After-treatment systems are employed to control the particle emissions from combustion engines. The design of the after-treatment system depends on the nature of particle size distribution at the upstream and is important to evaluate. In heavy-duty (HD) diesel engines, the turbocharger turbine is an important component affecting the flow and particles. The turbine wheel and housing influence particle number and size could potentially be used in reducing particle number or changing the distribution to become more favourable for filtration. This work evaluates the effect of HD diesel engine’s turbine on non-volatile particle number and size distribution.
This paper describes and compares different powertrain configurations for the retrofit of a heavy-duty Class 8 truck, powered by a 12.6 liters diesel engine. The engine is firstly equipped with an electrification-oriented organic Rankine cycle (ORC) system and then coupled to a traction electric machine into a hybrid powertrain. An electrification-oriented ORC system can produce enough energy to cover the ancillary loads, which in long-haul applications for freight transportation are quite demanding. Nevertheless, only powertrain hybridization can achieve significant improvements in the overall system efficiency. Both systems may thus be implemented in the same vehicle, but an efficiency improvement is guaranteed only if the system is carefully managed so as to reach a trade-off between the requirements and potential benefits of the ORC system and those of the hybrid powertrain.
Hydrogen is the most promising alternate fuel for Internal Combustion engines whereas its potential for Compression Ignition (CI) engine is unexplored. The addition of hydrogen to conventional hydrocarbon fuels is the best method to improve performance and emission of internal combustion engine. The present work aims to evaluate the effect of partial replacement of diesel with hydrogen in CI engine by means of hydrogen enrichment. Enrichment is achievedby introducing hydrogen with the intake air stream in intake manifold. The test engine used is 4-cylinder, water cooled 3.24L turbocharged diesel engine. Enrichment is achieved by retrofitting the hydrogen induction system in intake manifold. The hydrogen is continuously injected using mechanical injector associated with all safety equipment. The diesel and hydrogen mass flow rates are controlled to vary enrichment percentages from 2% to 8%. Also numerical base line engine model and hydrogen enriched model is developed in AVL Boost.
This work explores the influence of ethanol on improving engine's behavior of Waste Cooking oil (WCO) based dual fuel diesel engine. A single cylinder diesel engine was tested in dual fuel mode of operation at the maximum rated power output of 3.54 kW. In the current study a diesel engine is made to run using ethanol in dual fuel mode with diesel, where ethanol is introduced as primary fuel into the intake manifold and WCO as pilot fuel. The ethanol energy contents of the total fuel were varied from 5%, 10%, 15%, 20%,25%,30%,35% and 40% were experienced at (1500 ± 10) rpm of constant engine speed The test results showed the improvement in brake thermal efficiency (BTE) of the engine, reduction in brake specific fuel consumption (BSFC) with an increasing ethanol energy fraction. Furthermore, indicated specific NOx, CO, CO2 and smoke emissions decrease with an increasing percentage of ethanol energy content.
The current research work concentrate on the use of nano additive as a distinguishable thing for decelerating hazardous diesel engine emissions. The experiment was conducted with biofuel; there is no significance of engine modifications for using the biofuel. The surplus amount of oxygen integrated within the biofuel can able to generate higher combustion rate relatively it produces more NOx, the NOx burden can be reduced with the help of REGR (reformed exhaust gas recirculation). The reforming of exhaust gases causes the measurable generation of smoke, CO and HC. In order to reduce the formation of above emissions, the affordable and sustainable alternate identified from the present research, by citronella biofuel with 100ppm Cobalt Chromite nano additive. The scrutinized output enumerates that the substantial reduction in HC, CO, and BSFC with elevated EGT (exhaust gas temperature) achieved by CBN-REGR than the typical usage of the traditional CB-REGR system.
Compression-Ignition engines are widely used for irrigation purposes in rural areas, which produce more noise and vibrations. In this research, neat diesel and Pongamia biodiesel blend (B20) was used to study combustion, noise, and vibration characteristics of an unmodified Genset compression ignition engine. Investigations were carried out in various load conditions from no load to full load. From the experimental results, it has been found that a strong correlation exists between the heat release rate and engine noise. The heat release rate is directly proportional to the magnitude of the engine noise. The noise level has an increasing trend for diesel and a decreasing trend for biodiesel with an increase in load conditions. A maximum of 80.3dB and 78.3dB was observed at 60% loading conditions for diesel and biodiesel, respectively.
Environmental Control System (ECS) of an aircraft is a complex system which operates classically in an air standard refrigeration cycle. ECS controls the temperature, pressure and flow of supply air to the cockpit, cabin or occupied compartments. The air cycle system of ECS takes engine bleed air as input. Parameters like bleed air pressure and temperature, mass flow, the external factors like ambient temperature, pressure, and aircraft attitude affect the performance of ECS to a large extent especially during transient. So, it is very important to consider the transient characteristics of these parameters in the design stage itself in order to ascertain the dynamic response of the system. This paper explains in detail the importance of transient input characteristics during the detailed design of ECS. A typical temperature control scheme for combat aircraft ECS has been studied and modeled in LMS AMESim.