Heat exchangers are a prolific application found in all things that concern fluid and power; they are mission-critical applications that affect overall performance in aircraft of all sizes. Yet, for years, heat exchangers have been constrained, by traditional manufacturing, in terms of limited geometric freedom and lengthy lead times. Consider the following • Heat exchangers are commonly fabricated with stainless steel and then gold brazed, which can be extremely costly • Each weld joint costs $100; in traditionally manufactured fuel and high-pressure systems, there could be hundreds of welds • There can be a lack of integration with other systems like electrical motors or conformal cooling with batteries. Assembly integration, testing, and validation are lengthy and difficult. Additive manufacturing (aka 3D printing) has opened new possibilities for thermal conductivity and heat-exchanger design that enable end users to push the limits of what is possible.
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.
For improving the thermal efficiency and the reduction of hazardous gas emission from IC engines, it is crucial to model the heat transfer phenomenon starting from the intake system and predict the intake air’s mass and temperature as precise as possible. Previously the authors developed an empirical equation based on an experimental setup of an intake port model of an ICE in order to be implemented into the engine control unit and numerical simulation software for heat transfer calculations. The authors developed an empirical equation based on the conventional Colburn analogy with the addition of Graetz and Strouhal numbers. Introduced dimensionless numbers were used to characterize the entrance region, and intermittent flow effects, respectively.
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.
Abstract Metallic particles in brake-friction materials (FMs) play a vital role in improving mainly strength, friction level, thermal conductivity and hence resistance to fade and during braking operations. Although Copper was the most efficient and popular metallic ingredient in FMs, it is being phased out because of its proven threat to the aquatic life in the form of wear debris. Hardly any successful efforts are reported in open literature barring few on initial exploration of stainless steel swarf (SSS) and particles of stainless steel (SSP) in the authors’ laboratory. It is a well known fact that the size and shape of particles affect the performance of FMs apart from their type, concentration etc. In this research, Ferritic stainless steel (SS 434) particles were selected as a theme ingredient in two forms, first particulate (SSP) with two sizes, large (30-45 micron) and small (10-20 micron) and also in the form of swarf.
Graphite plays a crucial role in friction materials, since it has good thermal conductivity, lubricity and act as a friction modifier. The right type, amount, shape, and size of the particles control the performance of the brake-pads. The theme of the study was investigating the influence of size of graphite particles (having all other specifications identical) on performance properties of brake-pads containing graphite particles in the average size of 60 µm, 120 µm, 200 µm and 400 µm. Physical, mechanical and chemical characterization of the developed brake-pads was done. The tribological performance was studied using a full- scale inertia brake dynamometer following a Japanese automobile testing standard (JASO C406). Tribo-performance in terms of fade resistance, friction stability and wear resistance were observed best for smaller graphite particles. It was concluded that smaller size serves best for achieving best performance properties barring compressibility.
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 temperature distribution in disc brake mounted within in-wheel motor driven vehicle has several negative effects on braking performance. This is mainly due to the enclosed nature of the braking system. This paper aims to determine the effect of contact geometry on temperature distribution and thermal buckling in such a brake. Numerical analysis is conducted to investigate the variation of temperature field on the brake disc at different cover angles of pads while maintaining the same moment of friction. The effect of different radial positions of the pads is a second consideration in the current work, using a transient modeling approach. To validate the simulation results, an approximate, analytical solution is derived according to energy conservation. The results show that, for the same work done by the pads, the maximum temperature on the disc increases with a decrease in the pad cover angle.
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.
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 sub-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 SAE 2018-01-0121, the conventional pressurized motored method was investigated and compared with other friction determination methods. The pressurized motored method proved to offer a good intermediate between the conventional motored tests, which offer good repeatability, and the fired tests which provide the real operating conditions, but lacks repeatability and accuracy.
The electrochemical performance of a lithium-ion battery is strongly affected by the temperature. During charge and discharge cycles, batteries are subjected to an increment of temperature that can accelerate aging and loss of efficiency if critical values are reached. Knowing the thermal parameters that affect the heat exchange between the battery surface and the surrounding environment (air, cooling fins, plates, etc…) is fundamental to their thermal management. In this work, thermal imaging is applied to a laminated lithium-polymers battery as a non-invasive temperature-indication method. Measurements are taken during the discharge phase and the following cooling down until the battery reaches the ambient temperature. The 2d images are used to analyze the homogeneity of the temperature distribution on the battery surface. Then, experimental results are coupled with mathematical correlations.
The Indian automotive industry has migrated from BS IV (Bharat stage IV) to BS VI (Bharat Stage VI) emission norms from 1st April 2020. This two-step migration of the emission regulations from BS IV to BS VI demands significant engineering efforts to design and integrate highly complex exhaust after-treatment system (EATS). In the present work, the methodology used to evaluate the EATS of a high power-density 1.5-liter diesel engine is discussed in detail. The EATS assembly of the engine consists of a diesel oxidation catalyst (DOC), a diesel particulate filter with selective catalytic reduction coating (sDPF), urea dosing module and urea mixer. Typically, all these components that are needed for emission control are integrated into a single canning of shell thickness ~1.5mm. Moreover, the complete EATS is directly mounted onto the engine with suitable mounting brackets on the cylinder block and cylinder head.
In this paper the heat transfer coefficient and the heat transfer rate of a heat exchanger is scrutinized by using nanofluids. The silicon carbide nanoparticles, milled and sonificated as nanofluids of volume fractions 0.01499(%) and 0.01399(%). The heat transfer characteristics of SiC(P)/water, SiC(M)/water, SiC(P)/EG, SiC(M)/EG are measured in a concentric tube heat exchanger under laminar flow condition. The consequence of nanoparticle physiognomies, Reynolds number, on the heat transfer characteristic is scrutinized. It has been found that the addition of milled nanoparticlein the base fluids enhances the heat transfer characteristics rather than the normal nanoparticle. The experimental results shows that the heat transfer characteristics of SiC(M) is higher than that of SiC(P) in both the case of water and EG. This is because of the structural changes of SiC-M by the deformation caused by the ball milling.
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.
The enormous need of effective transportation creates an unavoidable situation in automobile industries to improve and maintain safety systems in vehicles. In crisis, brake disc of the braking system plays a vital role in effective braking of the vehicle. The main objective of this proposed study is to design a disc with two different groove patterns and a material with two different compositions. By using solidworks, a brake disc with proper slots and groove pattern (J hook and square groove) was designed for improved bite, debris, clearance, reduced distortion / vibration and effective heat transfer through convection process. In which two different materials namely zinc based Aluminium Alloy (AA8011) and its composite (AA8011 (5 wt% B4C +3 wt% Gr)) are considered after heat treatment (T6) as disc materials. The properties are measured and given as input data set in ansys workbench for further processing.
The SAE formula student car organization constrained a rule to place a restrictor of diameter 20mm in between the throttle body and the engine inlet. The restrictor is a component that reduces and regulates the mass flow of air into the engine inlet. For this, a venture nozzle will be used as a restrictor in a vehicle to decrease the air pressure and increase the velocity in the intake manifold. Our proposed work aims to minimize the pressure drop by changing the convergent and divergent angles in the restrictor. For this by using solidworks eight various combinations of models with convergent angle as 13, 15 degrees, and divergent angle as 5,7 degrees was designed and analyzed using CFD fluent in ansys work bench. In this, 13 degree as convergent and 5 degree as a divergent model was found to have laminar airflow throughout with optimum pressure drop. The plenum is a large duct that equalizes the pressure drop caused by the restrictor in order to improve the efficiency of the engine.
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 governments 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 in India, it is necessary to make such options comfortable and cost-effective. One of the most effective way to make shared mobility options cost effective is to comfortably increase occupancy per vehicle footprint. This paper aims to evaluate a novel method of occupant seating to identify the maximum number of passengers a vehicle can accommodate without significant impact on occupant comfort. It is assumed that shared mobility options are used for a short duration of commute, and hence the comfort of the seat can be marginally compromised to increase the total number of occupants.