In industrial processes, combustion engines and co-generation plants, large amounts of waste heat are generated, which are often lost to the environment. The conversion of this thermal energy into mechanical work and ultimately into electrical power promises a significant improvement in energy utilization, the efficiency of the overall system and, consequently, cost-effectiveness. Therefore, the use of a Rankine Cycle is a well-established technical process. A recent research project investigates a novel expansion machine to be integrated into an RC-process to convert the heat energy into mechanical work. Primarily, the present work deals with the fluid dynamic simulation of this expander, which is based on the principle of a rotary piston engine. The aim is to develop, analyze and optimize the process and the corresponding components. Hence, a CFD model has to be built up, which should correspond as closely as possible to the requirements and geometries of the physical engine.
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.
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.
High speed on-off valve under the control of high frequency pulse width modulation (PWM) can make control linearly as proportional valve does. It is because its valve opening is adjusted linearly by duty ratio within a certain range. It is significant for high speed on-off valve to achieve precise linear control performance. In practice the performance is influenced not only by control strategy, but also the structural parameters of the valve, such as seat angle, spool diameter of valve and so on. In this paper, it is indicated that the effects of structural parameters on linear control performance of high speed on-off valve is exerted by flow force since different structural parameters bring about different valve opening-flow force characteristics. Accordingly, the relationship between the valve structural parameters and flow force is emphasized.
In addition to the typical broadband noise character of wind noise, tonal noise phenomena can be much more disruptive, regardless of the overall interior noise quality of the vehicle. Whistling sounds usually occur by flow over sharp edges and resonant gaps, but can also be caused by the feedback of sound waves with laminar boundary layers or separation bubbles and the resulting frequency-selective growth of boundary layer instabilities. Such aeroacoustic feedback can e.g. occur at the side mirror of a vehicle and one compellingly needs the coupling of acoustic and flow field. A compressible large eddy simulation (LES) is in principle suitable but one has to take care of any numerical artifacts which can disturb the entire acoustic field. This paper describes the possibility to resolve aeroacoustic feedback with a commercial 2nd/3rd order finite volume CFD code.
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.
An effective technology to reduce emission and fuel-consumption is the use of turbochargers. A turbocharger increases the air pressure at the inlet manifold of the engine by using the waste energy from the exhaust gas to drive a turbine wheel that is linked to the compressor through a shaft. Besides the use in combustion engines, fuel cell systems for vehicle applications also need compressed air to achieve high power densities. Thereby, in fuel cell systems the noise emission of turbochargers is no longer masked by the combustion engine. In operation, the main noise sources are generated by the flow in the compressor and the different noise phenomena need to be understood in order to efficiently reduce the emitted noise and increase comfort. A huge potential in order to achieve this goal is a simulation based investigation to study in detail the flow mechanism, the aeroacoustic sources and its sound propagation.
Some hybrid powertrains utilize an engine to benefit from the power density of the liquid fuel while the electric machine; for transient needs, for very low loads and where legislation prohibits any gaseous and particulate emissions. Consequently, the operating drive cycle of an engine also shifted from its conventional, broad range of speed and load to a narrower operating range of high thermal efficiency. This requires a drastic departure from conventional engine architecture, meaning that analytical models used to predict the behaviour of the engines early in the design cycle are no longer always applicable. Friction models are an example of sub-models which struggle with previously unexplored engine architectures. The pressurized motored method has proven to be a simple experimental setup which allows a robust FMEP determination against which engine friction simulation can be fine-tuned.
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.
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 SAE organization constrained a rule to place a restrictor of diameter 20mm in between the throttle body and the engine inlet . The restrictor is an component which reduces and regulates the mass flow of air into the engine inlet. For this a venture nozzle will be used as a restrictor in vehicle to decrease the air pressure and increase the velocity in the intake manifold . The aim of our proposed work is to minimize the pressure drop by changing the convergent and divergent angles in the restrictor. For this by using solidworks sixteen various models with convergent angle as 11,13,15,17 degrees and divergent angle as 3,5,7,9 degrees was designed and analysed using CFD fluent in ansys work bench. In this 13 degree as convergent and 5 degree as divergent model was found to have laminar air flow through out with optimum pressure drop. The plenum is a large duct which equalise the pressure drop caused by restrictor in order to improve the efficiency of engine.
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.
Aerodynamic CFD simulations are effectively used to cut down the vehicle development period and to completely understand the aerodynamic effects on vehicle performance. Attaching add-on devices to improve aerodynamic performance is the approach which is highly followed. While the methodologies are well established to quantify the effect of add-on device on improving drag coefficient of a vehicle, the investigations still require in depth understanding, even though a vast number of studies available on aerodynamic drag performance improvement. Front air-dam is one of the components attached below the front bumper to reduce airflow towards underbody and away from front tires, to reduce drag coefficient. However, the size and position of front air-dam must be optimized to get the desired result. Extensive iterations are carried out to finalize the front air-dam size and position until the target is achieved.
Transportation system is at the brink of revolution and many new ways of mobility are arising in the market to ease the pressure on the established transportation infrastructure. Many companies and government around the world are exploring innovative options in the space of shared mobility to reduce the overall carbon footprint. To expedite the adoption of shared mobility based travelling options in India, it is necessary to make such options comfortable and cost-effective. To make the mobility option cost-effective, it is important to comfortably allow as many passengers per vehicle foot-print as possible. This paper aims to evaluate a novel method of occupant seating to maximize the number of passages the vehicle cabin can accommodate. Since shared mobility options are used for a short duration of commute, the comfort of the seat can be compromised for increasing the no. of occupants. This paper studies the relation between occupant comfort and the inclination of seat cushion.
Sealing is one of the important components in automotive and aerospace industry. The primary function of lip seal is to protect contamination and retaining the lubricant. This investigation relates to study of contact pressure existence on dynamic sealing. Sealing for steering intermediate shaft requires sliding motion between shaft and seal as well as protection of lubricant from contamination and retention. Contact pressure analysis of Steering intermediate shaft with hyper elastic rubber seal is done at static as well as sliding condition using ABAQUS. Experiments were also conducted to check contact pressure between seal and shaft by using Fuji-pressure film sensor. The result from CAE analysis was compared with experimental data. This analysis of contact pressure helps to support enough interference between seal and shaft with satisfies the need of sealing as well as sliding in intermediate shaft.
Vehicles are main source of pollution contributor, producing substantial amounts of pollutants. Pollution causes the health problems, hence Emission legislations are becoming increasingly strict all over the world moving from Trem IIIA to Stage V for Off-highway vehicles. EGR has been successfully proved as a useful technology to reduce NOx by decreasing the oxygen concentration and the peak temperature of the combustion. Due to compact design and space restriction, the distance required for the homogeneous mixing of fresh air and EGR is not enough. Therefore the mixing of the EGR and distribution of the EGR over the cylinders is not equal.