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.
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.
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.
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.
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.
Abstract: Attapulgite, a unique clay mineral is a crystalloid hydrous magnesium-aluminium silicate, composed of silicon oxide, aluminium oxide, magnesium oxide, iron oxide etc. having formula Mg5Si8O20(HO)2(OH2)4•4H2O. Its structure is somewhat between laminated and chain structure having very high surface area and porosity. Its magnesium silicate structure resembles a brick wall with every second brick missing. This leaves elongated porous channels that are highly absorbent. Its fibers were proven to be excellent substitute for asbestos in brake-pads. Hardly anything in details is reported on its exact role in controlling tribo-properties of friction materials (FMs) especially Cu-free FMs. Hence, in this work a series of brake-pads with five types was formulated and developed with increasing amount of attapulgite (0, 5, 10 and 15 wt. %) by compensating with inert barite particles in Cu-free FMs.
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.
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-ion 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.
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.
The implementation of increasingly stricter regulations on CO2 emissions by the European Community is pushing the automotive industry towards a radical change. In a rush to electrify their model ranges, global carmakers are investing heavily on developing new electrified powertrains. Within this context, this work focuses on the analysis of electric axles drives (eAxles) for a BEV (battery electric vehicle) sport car, with the aim to develop an analytical tool useful to perform predictive analysis in the concept design phase. Through a parametric definition of the procedure, the tool with its 2800 lines of code is able to “adapt” to any drivetrain layout analysed. The tool actually allows to enter more than 100 input values including lubrication conditions (oil viscosity and operating temperature), gears (number, macrogeometry, mesh), bearings (number, type, geometry, mounting layout, angle mesh), shafts, oil seals, external layout and external fluid conditions.
Piston is the most imperative part of an automotive engine in which it exchanges drive due to expanding gas in the cylinder to the crankshaft through the piston rod. During the combustion of fuel charge inside the ignition chamber, high pressure and temperature are developed and the piston is imperiled to high mechanical and thermal stresses. The main objective of the proposed work is to analyse the stress distributions and thermal behaviour of uncoated A356 - 5% SiC - 10% Fly ash HMMC piston crown and Plasma sprayed Yttrium Stabilized Zirconia(Y-PSZ) coated A356 - 5% SiC - 10% Fly ash HMMC piston crown. A356 - 5% SiC - 10% Fly ash HMMC were fabricated via squeeze casting to improve the performance of a petrol engine. A structural model of an HMMC piston crown was made using CREO software and structural and thermal analysis was done using ANSYS. Further coupled field analysis is done to find the stress and temperature distribution on the piston.
Recent years, researches are more focused on various enhancement methods for compact heat exchangers without altering the surface area of the heat exchangers. The advancements in the area of Nano fluids with better thermal properties have helped in development of light-weight, highly efficient automobile radiators. The main objective of this project is to increase the thermal performance of the radiator and thereby reducing the size of the radiator. In this project a numerical model with porous medium approach was developed and validated. Nano fluids (Aluminium oxide, Copper oxide, Graphite) of different volumes (ranging from 1%-13% in an interval of 2) are used along with water and it was observed that the heat transfer rate of the radiator is increased by 4.49% and the volume of the radiator is reduced by 5.4% for the addition of 5% of Aluminium oxide in water.
The pattern of utilizing the water/diesel emulsion fuels in engines has been given great importance due to its eco-friendly nature and minimal exhaustion of petroleum reserves. This investigation displays the impact of 1,4-dioxane emulsified fuel on performance and emissions at various operating pressures. 1,4-dioxane emulsified fuel (DWA10) was prepared with 10% 1,4-dioxane, 10% water, 0.2% surfactant and 79.8% diesel. To estimate the engine performance and emissions, the engine was operated with 180 bar, 200 bar and 220 bar operating pressures and the output was equated with diesel fuel operating on normal pressure of 200 bar. BTE of 1, 4-dioxane emulsified fuel at 220 bar was higher when compared with diesel fuel. CO, HC and BSEC were lower at 220 bar when compare with diesel fuel. However, NOx was found to increase for the higher operating pressure.
A waste heat recovery unit (WHRU) is an energy recovery heat exchanger that recovers heat from hot streams with high energy contents. In this study, the modification of the design of the waste heat recovery unit which receives flue gases from the boiler in order extract the heat from flue gases and enhance the heat transfer rate. Generally, the body of the waste heat recovery unit of the boiler is made up of Aluminium which receives exhaust gases from the boiler plant through two inlets of different sizes which connected to exhaust outlets of the plant. This unit assists to extract the heat from the flue gases with help of rubber jacket wrapped around it which has inlet and outlet for circulation of water in order to extract the heat from the flue gases. Due to wear and tear of the rubber jacket which leads leakage of the water and steam, leads to poor exchange of heat and hence needs frequent replacement instead of service.
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.