Marcelo López-Parra

DYNAMIC PERFORMANCE OF THE LEBLANC BALANCER FOR AUTOMATIC WASHING MACHINES

The paper describes a high-speed camera and a Particle Image Velocimetry (PIV) technique used on a transparent liquid balancing device for washing machines. Experimental results indicate that the baffle-liquid interaction renders fluid modes of vibration of circumferential and axial type. This complex swirl flow is comprised of two inertial waves; one of such waves is synchronous with the rigid body motion, while the other is a fluid backward traveling wave, thus enhancing the system damping capability. This damping phenomenon was revealed by the fluid flow visualization and Particle Image Velocimetry (PIV) technique employed. NOMENCLATURE

Liquid self-balancing device effects on flexible rotor stability

Nearly a century ago, the liquid self-balancing device was first introduced by M. LeBlanc for passive balancing of turbine rotors. Although of common use in many types or rotating machines nowadays, little information is available on the unbalance response and stability characteristics of this device. Experimental fluid flow visualization evidences that radial and traverse circulatory waves arise due to the interaction of the fluid backward rotation and the baffle boards within the self-balancer annular cavity. The otherwise destabilizing force induced by trapped fluids in hollow rotors, becomes a stabilizing mechanism when the cavity is equipped with adequate baffle boards. Further experiments using Particle Image Velocimetry (PIV) enable to assess the active fluid mass fraction to be one-third of the total fluid mass. An analytical model is introduced to study the effects of the active fluid mass fraction on a flexible rotor supported by flexible supports excited by bwo different destabilizing mechanisms; rotor internal friction damping and aerodynamic cross-coupling. It is found that the fluid radial and traverse forces contribute to the balancing action and to improve the rotor stability, respectively.

A Case Study in “Total Beauty” Design: An Experience Through Sustainable Product Design

Recent research on ‘engineering design’ is expanding to consider methods, tools and frameworks aimed at assisting designers in the process of developing sustainable products. Some of these new approaches highlight the importance and advantages of applying biology, chemistry and human-environment health, concepts and principles at the design stage of the product development process. The successful application of these approaches also requires overcoming a number of challenges. Two particular issues currently being investigated are: 1) the contradictory and sometimes misleading use of concepts regarding what a sustainable product is; and 2) the lack of sustainable parameters to evaluate how sustainable a product is. This paper presents a synthesis of the Total-Beauty theoretical framework, based on the study reported in a previous paper. Then, a process to redesign products using BioThinking, is proposed followed by its application in the redesign of a product. The process is original because it shows how the core concepts are considered in all the steps of a design process and not just in the specification and evaluation steps. The redesign is used as a case study to show its utility. The paper includes the synthesis of evaluation parameters based on BioThinking to both assess the sustainability of products, and compare the redesigned product against the original design. In the end of the paper, a discussion of the design process and the results of the case study will be presented.Copyright

Energy consumption analysis of ABS plastic parts injected in a hybrid injection moulding machine

ABSTRACT The energy analysis of injection moulding processes is influenced by complex interactions amongst the moulded part, its material, the injection machine, the process parameters and the environmental conditions. The availability of energy usage analyses that comprehend information on specific materials and machine kind is limited. This paper reports a study that estimates and analyses the power usage profile (PUP), the specific energy consumption (SEC), and the energy distribution at an operation level of two different injected parts made of acrylonitrile-butadiene-styrene and produced in a hybrid injection moulding machine. The methodology followed by the authors incorporates an experiment carried out in an industrial facility. A large sample size, and data-acquisition and data post-processing processes to obtain an accurate PUP and SEC are used. A breakdown of the energy consumed by the injection moulding process of the parts studied at an operation level using Sankey diagrams is discussed. The study results are used to identify strategies to reduce the energy consumed by the processes. The methodology employed, and the strategies reported could be used with other plastic parts regardless of the material and machine used. The results reported are new experimental data useful input for theoretical models.

Sustainability Assessment of Products: A Comparative Study of Sustainability Assessment Tools

The number of existing tools, principles and approaches to assess sustainability in products is growing to meet industry and society needs. For those related to design and development in universities, research institutes and companies it is a fundamental issue to recognize features and details of the sustainability assessment tools in order to select the one that best fits their particular needs. This paper describes the outcomes of a product sustainability assessment carried out at Universidad Nacional Autonoma de Mexico, UNAM. The approach followed by the authors in this assessment was aimed at comparing the results provided by a set of software tools and a previous sustainability integrated-criteria tool developed by the research group.The main contribution of this paper is the insight on the software tools used and on the results of the assessment since the design point of view. The results of the assessment included metrics such as: carbon footprint, energy use, end of life potential, toxicity, eco-toxicity, human toxicity, recyclability, and others. In the first part of the paper, an introduction of the criteria and the software based tools for sustainability assessment used by the authors is presented. Then a justification of the tools used and an explanation on how the comparison was achieved are given. The product used as a case study and the results of its sustainability assessment are presented. The case study part is a home appliance subsystem. In the end of the paper conclusions, insights and further work are given.Copyright

Current Situation of Design Criteria for Intervertebral Disc Prosthesis

This paper presents the literature review on the design criteria for intervertebral disc prosthesis. The design criteria relate to the design features that intervertebral prosthesis must accomplish (i.e. fixation to bones, spine mobility, energy absorption and etcetera). The need to improve the performance has led to changes in the features which reflect in the current design criteria.Currently, the disc prosthesis technology is experiencing a generational change. The first generation was thoroughly studied while the second generation is in the clinical tests stage. During the time the first generation prostheses were applied in patients there was not a clear trend in the clinical results which produced a lack of trust and reliability in the performance of the disc prosthesis. The changes in the design features of one generation compared to the next generation are based in the deepening in the knowledge of the problem and the results obtained with the first generation prostheses.Some design criteria were identified for the first generation. These criteria were not completely characterized since there was not enough information to be used by the designer. This lack of characterization of most design criteria produced many different versions without a clear focus which help to define the basic design features of disc prostheses. This document presents the necessary information to thoroughly characterize the design criteria outlining the missing information for the design criteria found. An analysis is done of the design criteria in the second generation of prosthesis.Finally if the information contained in the design criteria is enough, the clinical results would be better focused to achieve a more repeatable, reproducible and reliable process for a total disc intervertebral prosthesis replacement as now is considered the vertebral fusion, this is a gold standard.Copyright

Teaching Sustainable Design Within a Product Innovation Process in Mexico: Linking Two One-Semester Design Courses

This paper documents the process, the outcomes and the lessons learned from two design courses aimed at incorporating environmental, economic and social concerns during the product development process. These courses are co-taught by professors of the Engineering and the Industrial Design Schools of the Universidad Nacional Autonoma de Mexico (UNAM). Each course lasts one academic semester and includes engineering graduate and undergraduate students from industrial design and engineering.The two courses are “New Product Development” (NPD) and “Design for Sustainability” (DS). The NPD course runs in collaboration with the University of California at Berkeley (UCB) and it has been taught at UNAM since 2008. The course fosters the development of product concepts that address particular user needs related to sustainability issues and enhance user’s experience and innovation.The DS course is aimed at introducing students to the most representative approaches, methodologies and tools related to sustainability. DS takes the NPD process as a background, i.e. takes the NPD product concept produced by students and evaluates its environmental impact, and its technical and economic feasibility. Some issues on entrepreneurship and social responsibility are also covered.For both courses design projects are paramount. Some of the projects carried out by the students during the courses are proposed by students themselves and some others are put forward by companies.The first part of this paper includes some background information on representative sustainability courses reported in the literature. Then the complete process model comprised by the NPD and DS courses is presented. Some details of the actual courses contents and lecture activities are also described. Representative projects developed within the courses, one of which is now a startup company, are presented. Finally, insights and lessons learned are discussed.Copyright

Dynamic Analysis of a Bladed Balance Ring Device

Among the solutions to the rotor unbalance problem, the previous art shows the use of passive balancers. The liquid balance ring fall in this category, which basically consists of a hollow ring equipped with a number of anti-sloshing baffle boards inside the cavity. The liquid contained within the ring adopts an antagonist position to the unbalance, thus balancing the rotor. Nowadays, in regard to the shape of the baffles boards employed in liquid balance ring devices, the use of straight baffles is the standard practice. However, as the fluid is subjected to rotation, it makes sense to believe that there should be a better baffle shape to enhance the fluid-solid interaction and improve the balance ring dynamic performance. This research work introduces for the first time a balance ring with curved (forward and backward) blades that remarkably enhance the unbalance response of rotors in the transient and steady-state. A classical dynamics model of this novel bladed concept is introduced and employed in designing a liquid balance ring for high-speed performance. Experimental data showing good correlation between the model and tests is presented.Copyright

International and Multidisciplinary Experiences in Engineering Courses at UNAM

A team of faculty members from the Universidad Nacional Autonoma de Mexico (UNAM) has coordinated multidisciplinary courses in collaboration with universities from other countries. The team, who is composed by faculty from the School of Engineering and the School of Architecture, coordinates with pairs of Stanford University, the University of California at Berkeley, and the Technical University of Munich; to teach three particular design courses.All three courses are related to product innovation but they have different emphasis depending on the collaborating partner. The focal points of each of the three courses are: (1) innovation, (2) user centered design and sustainability and (3) transport in megacities of the future.Engineering and industrial design students are involved in the courses. They are organized in teams that include participants from the two collaborating universities. During the courses teams carry out projects working mostly at a distance; they use different means of communication and information sharing and also pay reciprocal visits between the universities involved in the collaboration.This paper describes each of the three courses highlighting their particular characteristics. The outcomes and results of the courses and specific projects are commented. In the end of the paper lessons learned are discussed and final remarks are presented.Copyright

Stability of Flexible Rotors With a LeBlanc Balancer

Although the liquid balancer has nearly a century of having been introduced by LeBlanc, little information is available on the dynamic response and stability behavior of this kind of device. Earlier author’s research using a high-speed camera and a Particle Image Velocimetry (PIV) technique showed the existence of a fluid backward traveling wave inside the balancer cavity. This damping phenomenon helps enhance the unbalance response of the rotating system and also raises the stability limits. This paper shows that a flexible rotor employing a LeBlanc balancer has remarkable increase in the threshold speed of instability for aerodynamic cross-coupling and viscous internal friction damping.Copyright