Adaptive structures for whole-life energy savings

The design methodology described in this paper takes a substantial shift from conventional methods. Traditionally sizing is based on the worst expected load scenario. By contrast to this conventional passive approach the method presented here replaces passive member strategically with active elements (actuators) which are only activated when the loads reach a certain threshold. The structure can withstand low level of loads passively. Above the threshold, actuation comes in to allow the structure to cope with high but rare loading scenarios. Active control introduces operational energy consumption in addition to the energy embodied in a passive design. In this paper we use this dual design to minimize the overall energy required by the structures. This methodology has been used on a simple truss structure and it was showed that it allows significant weight saving compared to conventional passive design. We extend the application of the methodology to a more complex 3D structure. It is confirmed that an optimum activation threshold exists that leads to design that minimises the total energy of the structure. Compared to an optimised passive design we show that the total energy saving is 10-fold

Pumping vs. iron: Adaptive structures for whole life energy savings

The design methodology explained in this paper takes a substantial shift from conventional methods where sizing is based on a single load case i.e. the maximum expected load. The difference from a conventional passive approach is that strategically located elements of the system provide controlled output energy (actuators) in order to manipulate actively the internal flow of forces and stresses. In this way stresses can be homogenized and deflections kept within desired limits. The alternative we are proposing offer a way to actively counteract loads when needed. Two dimensional pin-jointed trusses designed using this methodology show that substantial weight savings can be achieved respect to optimised "passive" structures (designed using Fully Utilised Design method).While the decrease in mass through actuation leads to reduction of embodied energy, it increases the operating energy that the active elements need to provide. Whole life energy analysis, implemented as coupled optimization between embodied and operating energy, reveals that an optimal trade-off exists. Results show that energy savings remain significant even considering the operating energy of the actuators for the entire life-cycle of the structure. © 2011 IEEE

Experimental and Numerical Investigation of a Direct Injection Spark Ignition Hydrogen Engine for Heavy-Duty Applications

International audienceThe H2 internal combustion engine is gaining increasing interest especially for commercial vehicles. Regarding the optimization of the combustion process, results of experimental investigations on a H2 heavy-duty single-cylinder engine in combination with numerical 3D-CFD investigations are presented. In addition to a Direct Injection (DI) Spark Ignited (SI) configuration, Port Fuel Injection (PFI) is explored to provide a reference with near homogeneous cylinder charge. The main objective is to assess a 3D-CFD-RANS framework based on ECFM and state-of-the art sub-models to describe the most important phenomena occurring in H2 spark ignition engines and to support the experimental analysis. Experimental results show that the PFI configuration provides efficiency and emissions benefits at the expense of volumetric efficiency. The proposed CFD model demonstrates the ability to successfully simulate different engine operating conditions for both PFI and DI systems. In particular, it is shown that the charge stratification typical for DI systems is not beneficial for the studied configuration as it increases wall heat losses and NOx formation

Transport coefficients in thermal plasma : application to Mars and Titan atmospheres

this work is a contribution to the calculation of the transport coefficients for Nitrogen, hydrogen, mars and titan atmosphere plasma.ESA Technical Research Programme – TRP “Validation of Aerothermochemistry Models for Re-Entry Applications