Search results

High-pressure die casting is one of the manufacturing techniques used for the rational mass production of metal parts. Due to the high velocity of the molten metal during the injection phase, the die casting of aluminum is so complex and it is almost impossible to calculate these exact performances. Numerical simulation is an effective way to optimize the injection phase and minimize air entrapment that causes porosity defects in the metal. Generally, the filling phase of the molten metal in the shot sleeve is neglected in most scientific work. This phase is followed by a rest period to allow the escape of the resident air bubbles (gravity effect). The paper aims to discuss these issue.

It is relatively clear that the model described poses a great challenge for numerical implementation, especially for 3D geometries. The governing transport equations are solved numerically using the commercial CFD solver Fluent and the equations are discretized using a pressure-based finite volume method. The coupling pressure–velocity was solved by the PISO algorithm. The PISO algorithm takes relatively more CPU time per solver iteration, but it significantly decreases the number of iterations required for the convergence of the transient flow problems. Laminar flow inside air and molten metal was assumed. In order to describe the behavior of the molten metal, a VOF model has been activated. The model makes it possible to account for the moving boundary due to the variation of the shot sleeve volume caused by the plunger displacement. The scheme used in the discretization of momentum equation was the first-order upwind scheme, and the scheme used for the pressure was the PRESTO. The profile of the plunger velocity, boundary conditions change with time and the physical properties change with liquid fraction were used by implementation of a user-defined function. For the discretization of the domain, an unstructured mesh with triangular elements is used. After conducting mesh sensitivity study, a mesh having 53,813 triangular elements has been chosen for the present study. The convergence criterion was set equal to 10–4 for all parameters.

The results show that the rest and global filling times increase by 2.5 and 8.57 percent with decreasing the pouring velocity by 10 percent. In addition, the rest and global filling times decrease by 5.77 and 8.12 percent with increasing the pouring velocity by 10 percent.

After the filling phase, it is necessary to offer a rest period before the injection phase. However, the rest and global filling times increase by 2.5 and 8.57 percent with decreasing the pouring velocity by 10 percent. In addition, the rest and global filling times decrease by 5.77 and 8.12 percent with increasing the pouring velocity by 10 percent. Increasing the pouring velocity by 10 percent leads increasing of the molten metal velocity in the shot sleeve and requires a delay of time of the beginning of the faster plunger movement by 7–10.5 percent. On the other hand, Figure 12 shows that increasing the pouring velocity requires increasing of the plunger velocity during the injection phase, thus increasing the pouring velocity. In order to overcome this problem, it is necessary to reduce the injection velocity and prolong the period of the slower plunger movement.

The purpose of this study is to investigate the influence of dimple radius, depth and density on the lubrication performance of the plunger.

A lubrication model was adopted to consider eccentricity and deformation during the working process of the plunger, and a rig test was performed to confirm the simulation results. The texture was fabricated using laser surface texturing.

The simulation results suggested that when dimple radius or depth increases, oil film thickness of the plunger increases before decreasing, and asperity friction displays an opposite trend. Therefore, appropriate microdimple texture could facilitate lubrication performance improvement and reduce the wear. Microdimples were then lased on the plunger surface, and a basic tribological test was conducted to validate the simulation results. The experimental results suggested that the average friction coefficient decreased from 0.18 to 0.13, a reduction of 27.8%.

The introduction of microdimple on a plunger couple to reduce friction and improve lubrication is expected to provide a new approach to developing high-performance plunger couple and improve the performance of the internal combustion engine. If applied, the surface texture could help reduce friction by around 27% and cap the cost relative to the plugger friction.

The microdimple texture was introduced into the plunger couple of a vehicle to reduce the friction and improve the performance. Findings suggested that surface texture could be used in the automotive industry to improve oil efficiency and lubrication performance.

The peer review history for this article is available at: http://dx.doi.org/10.1108/ILT-07-2020-0259.

THE Junkers 211B engine is one of the three large liquid‐cooled aircraft engines known to be produced in quantity in Germany. It powers the Junkers Ju 88 and Heinkel He 11 IK twin‐engined bombers, the Junkers Ju 87B single‐engined dive‐bomber, and the Focke‐Wulf Fw 200K long‐range 4‐engined bomber, altogether an impressive percentage of the Luftwaffe.

Scavenging air enters a two‐stroke cylinder by tangential ports e3 and exhaust leaves by one or more ports in a substantially cylindrical combustion chamber a3 into which liquid fuel is injected by a transversely‐arranged injector c. A shoulder aa2 is closely approached by the piston, the clearance being thus limited to the combustion chamber a3 which preferably contains one large exhaust valve b. Air is supplied by a blower to a chamber e. The injector c may have a single orifice and be radial or tangential to the chamber a3.

AS far as we are concerned at present in England, there are only six types of German aeroplanes which are of any interest. These are:—

The first part of this section deals in general with considerations of engine design, and the latter part with the effects of engine operating conditions.

When the Martin‐Baker Mk. 10 ejection seat was introduced into service, it established significant improvements over earlier seats in many aspects of performance. In the years since that time, it has been adopted by air forces all over the world and has demonstrated the high degree of reliability associated with this company. Of the many types of aircraft in which the seat is installed, the Panavia Tornado, for example, has the 10A, the RAF Hawk the 10B and the Royal Navy Sea Harrier the 10H, each of these being individually suited to particular requirements.

FROM the conventional wartime under‐carriage consisting of a straight through axle suspended on bracing struts by shock absorber cord has developed the complex modern undercarriage which is required to absorb the energy of descent, provide smooth taxying and the braking effort, and disappear when not in use. These requirements have brought in their trail a collection of hydraulic, pneumatic and electrical auxiliaries and a comprehensive treatment of the subject would assume some magnitude. This paper therefore summarises existing practice to some extent, and presents some notes on various design aspects which, it is hoped, will prove informative.

A GREAT deal of development has already been made in the technique of drawing iron, steel, brass, copper and aluminium, whereas the drawing of light alloys—particularly those, like duralumin, of high strength values is still in need of further development.

PREVIOUS articles in this series have dealt with centralized systems of automobile chassis lubrication that are available to motor vehicle manufacturers for fitting to private motor cars, buses and commercial vehicles. We have covered systems whose operation depends upon air and vacuum, variations in manifold temperature, pedal operated, and also a mechanical unit that is driven by cable.