Browse Topic: Aluminum engines
Downsizing and Light weighting is the latest trend in the automotive industry to achieve more fuel efficient, compact and cost effective design of vehicles. Powertrain components compromise of more than 45% of the total vehicle weight. Automakers are putting significant efforts to reduce the weight of power train components. Integrated design of aluminum Engine Head and Intake manifold has been successfully implemented. Now currently we have identified the gear box housings for downsizing in light duty trucks i.e. Existing light duty trucks Cast Iron transmission. This design has been successfully modified with integrated clutch housing and transmission housing, using lightweight aluminum as the new material, using simulation tools. This lead to weight savings of up to 30% and cost savings of 20-25% as compared to existing cast iron designs. Using an integrated design reduces the assembly cost, makes the design more compact and gives better weight balance. From an emissions perspective, it is estimated that every 50 Kg of weight reduced from an average 1,500 Kg vehicle cuts CO2 emissions by 4 ~ 5 grams. This feat is achieved using simulation tools and experimental verification in three steps. First step is comparing the stiffness values of existing cast iron design with the new aluminum integrated design, step two is to optimize the design using topology optimization tool to achieve the most optimum weight of the housing. Step three is to analyses the housings strength in static, dynamic and fatigue loading conditions. The same is being backed by conducting experimental verification and these results has been correlated with the simulation results. The stiffness tests at the test rig have been successfully completed and the stiffness vales have matched with 98% accuracy with the CAE simulation results. The same housing is checked with RLDA tests and has been successfully completed all the requirements. Accelerated Endurance Test is also done on the vehicle with new housing to verify the design in running conditions as well. The FE simulation tools have helped us in selecting the right parameters for the design and ensure first time right design at the development phase. For future this can be implemented on light duty buses as well. The design and ensure first time right design at the development phase.
Thermally sprayed coatings have used in place of iron bore liners in recent aluminum engine blocks. The coatings are steel-based, and are sprayed on the bore wall in the liquid phase. The thermal response of the block structure determines how rapidly coatings can be applied and thus the investment and floor space required for the operation. It is critical not to overheat the block to prevent dimensional errors, metallurgical damage, and thermal stress cracks. This paper describes an innovative finite element procedure for estimating both the substrate temperature and residual stresses in the coating for the thermal spray process. Thin layers of metal at a specified temperature, corresponding to the layers deposited in successive thermal spray torch passes, are applied to the substrate model, generating a heat flux into the block. The thickness, temperature, and application speed of the layers can be varied to simulate different coating cycles. The temperature field in the block is calculated using a transient thermal analysis with convective cooling on exposed surfaces. The stresses in the coating are computed using a residual stress relaxation method. Computed temperature fields are compared to thermocouple measurements from two V8 blocks sprayed using the Plasma Transferred Wire Arc (PTWA) process the Ford Essex Engine Plant. Measured and computed peak temperatures agree well. The application of the procedure to eliminate a prototype thermal stress crack and to the investigation of torch paths is described.
A linerless aluminum (Al) engine block has potential to reduce the weight of an automotive engine and improve the fuel economy. However, the Al cylinder surface of an aluminum engine block is not usually strong enough to withstand the sliding wear against piston rings. A few surface processing technologies are used to protect the surface of cylinders. Among them, a thermal spraying coating, such as plasma transferred wire arc (PTWA) is already popular. Plasma electrolytic oxidation (PEO) coating is also proposed for increasing the wear resistance of aluminum-silicon (Al-Si) alloys and reducing the friction between the cylinder and piston. In this work, two different PEO coatings with a thickness of around 23 μm were prepared on an Al-Si alloy A356, and a high speed pin-on-disc tribometer was used to study the tribological behavior of the coatings at oil lubricant conditions. A cast iron sample was also used to do similar tribological tests for comparison. The coefficient of friction (COF) vs surface roughness (Ra: 0.2 - 0.8 μm) and sliding speeds (up to 6.07 m/s) were particularly studied. The results show that the COF significantly decreased with the increase of sliding speeds, and a smoother coating surface generally exhibited a lower COF and a steeper descent rate of the COF. While such observations seem true for both PEO coatings and the cast iron sample, the polished PEO coatings can have a lower COF than cast iron. The study indicates that the Al-Si alloy with PEO coatings could be further explored as a feasible solution to reduce the weight and improve the fuel efficiency of an Al engine.
Aluminum engines have been successfully used to replace heavy gray cast engines to lighten the car's weight and reduce the fuel consumption. To overcome the aluminum alloys' poor wear resistance, cast iron liners and thermal spraying coatings were used as cylinder bore materials for wear protection. A plasma electrolytic oxidation (PEO) technique had also been proposed to produce an oxide coating on aluminum cylinder bore. The oxide coating can have a low coefficient of friction (COF) and minimum wear shown in the lab tests. To conserve more fuel, the stopping and restarting system was introduced when the vehicle was forced to stop immediately for a short time. When the engine was forced to stop and restart, the reciprocating speed of the piston was very slow, and the friction between the piston and the cylinder was high. In this research, a pin-on-disc tribometer was used to investigate tribological behavior of the oxide coating on an aluminum alloy. The rotational velocity of the tribometer was increased stepwise in a low speed range during the tests. The COF and wear of counterface pins were measured and evaluated corresponding to different combinations of sliding velocities. The results showed that the COF could be affected by many factors such as coating composition, surface roughness, amount of lubricating oil and sliding velocity. With the increase of velocity in the low speed range, the COF decreased. The smoother of the coating surface, the less wear of counterface pin. A proper combination of coating surface roughness and sliding velocity could provide a significant lower COF and less wear.
In recent years, light weight components have been an area of significant importance in automotive design. This has led to the replacement of steel and cast iron with aluminum alloys for many automotive components. For instance, Al-Si alloys have successfully replaced nodular and gray cast iron in the production of large automotive components such as engine blocks. However, excessive residual strain along the cylinder bores of these engine blocks may result in cylinder distortion during engine operation. Therefore, in this study, neutron diffraction was used to evaluate residual strain along the aluminum cylinder bridge and the gray cast iron liners of distorted and undistorted engine blocks. The strains were measured in the hoop, radial, and axial orientations. The results suggest that the residual strain along the aluminum cylinder bridge of the distorted engine block was tensile for all three measured components. Conversely, the undistorted engine block had compressive strains in the axial and radial orientations, while the hoop direction had tensile strain of lower magnitude. The gray iron liners, meanwhile, had compressive residual strain for both engine blocks. The variation in strain, specifically in the aluminum cylinder bridge, suggests that permanent dimensional distortion in the cylinders was triggered by tensile residual stress when exposed to service conditions.
Rising fuel prices and more stringent vehicle emissions requirements are increasing the pressure on engine manufacturers to utilize technologies to increase efficiency and reduce emissions. As a result, interest in cylinder surface coatings has risen considerably in the past few years. Among these are SUMEBore® coatings from Sulzer Metco. These coatings are applied by a powder-based air plasma spray (APS) process. The APS process is very flexible, and can process materials which wire-based methods cannot, particularly metal matrix composites and pure ceramics. Applications range from small 2-stroke engines, motorcycles, and lightweight passenger car engines, up to high-speed diesel truck engines and medium-speed diesel engines. The compositions of the coatings can be tailored to the specific challenges in an engine, e.g., excessive abrasive wear, scuffing, corrosion caused by adulterated fuel, improved heat transfer from the combustion chamber into the water jacket, etc. A number of engines have been tested successfully. Most of them exhibited significant reductions in lube oil consumption (LOC), reduced fuel consumption, very low wear rates and corrosion resistance on the liner surfaces. This coating solution has been commercialized in various markets. It has proven to be suitable for mass production on both new engine blocks and liners, and for repair of worn-out parts. Such coatings will continue to play an important role when it comes to reductions of weight and emissions in internal combustion engines. An example of such a coating solution will be outlined. It has been carried out in collaboration with BRP Powertrain in Austria on a 1.5L 3-cylinder aluminum engine and together with the adjustment of the ring package and the piston a reduction of 35% in LOC was achieved. This engine will go into production in September 2012 with limited numbers coated in the Sulzer Metco Wohlen facility in Switzerland, until an engineered coating system is ready on site to start large series production. More details on the engine performance and design changes made to the cast aluminum block in order to take full advantage of the coating on the cylinder running surfaces is presented in the paper from Zorn et al.
Development of lightweight alloys suitable for automobile applications has been of great importance to the automotive industry in recent years. The use of 319 type aluminum alloy in the production of gasoline engine blocks is an example of this shift towards light alloys for large automobile components. However, excessive residual stress along the cylinder bores of these engine blocks may cause problems during engine operation. Therefore, in this study, neutron diffraction was used to evaluate residual stresses along the aluminum cylinder bridge and the gray cast iron liners. The strains were measured in the hoop, radial, and axial orientations, while stresses were subsequently calculated using generalized Hooke's law. The results suggest that the residual stress magnitude for the aluminum cylinder bridge was tensile for all three measured components and gradually increased with cylinder depth towards the bottom of the cylinder. The residual stress in the gray cast iron liner was highly compressive with a relatively constant stress magnitude.
IC Engine manufacturers are constantly in pursuit of better sealability of cylinder head and engine block interface for meeting performance and durability targets. In order to overcome variation in torque - tension characteristics of cylinder head bolt because of friction variations, yield based clamping are being extensively adopted. Current study is done on torque - tension characteristics of a cylinder head bolt with a controlled quality. The paper enumerates the experimental setup representing a sub 1 liter all aluminum engine's head-block joinery. Studies on torque - tension characteristics of cylinder head bolt and the effect of sealing interface using a cost effective single layer steel gasket are being discussed in the paper. Subject work has led to a successful implementation of angular torque parameters on head bolts to meet functional and durability targets.
The fourth generation of Lexus' global flagship sets new standards in engineering, technical innovation, refinement, and workmanship. “Yet again, Toyota demonstrates excellence in execution, not only in the basics, but also in the introduction of new active safety technologies in advance of their competitors,” one reader wrote, in describing the Lexus LS 460, Automotive Engineering International's Best Engineered Vehicle for 2007. “Transmission, engine, steering, chassis, fuel system, and driver monitoring systems are all new-and represent significant advances over the previous model,” said another.
The automotive industry convened in Detroit in early January for the annual North American International Auto Show to introduce a number of new production and concept vehicles. Many of the concept vehicles drew on the past for inspiration, focused on sporty performance and lifestyles, or blurred even more the distinction between car, truck, and SUV. AEI editors review their engineering highlights on the following pages.
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