Experimental study of waste egress from collection vehicle

Engineering Technology programs focus on delivering a hands-on based engineering education. The students get introduced to the theoretical development of engineering concepts first. Then they apply the concepts to solve practical problems and test the concepts in carefully designed experiments carried out in appropriate facilities. One of the key areas of focus in the Mechanical Engineering Technology program at Arizona State University Polytechnic (ASU Poly) is Thermofluids where therodynamic and fluid dynamic concepts are addressed. The Graduate Degree (M.S.) program in the Mechanical and Manufacturing Engineering Technology (MMET) department at ASU Poly has a variety of activities ongoing in this important area. The graduate student typically works on applied research projects designed with educational and research objectives. Most of these projects involve theoretical and experimental elements. The present paper describes one such project underway in the MMET Department. The project addresses engineering design issues associated with a dry waste collection truck to reduce the potential for load egress during transit. One of the major problems associated with waste collection process, especially the light weight material collected for recycling, is that in the low speed transit segment of the operation, in which the vehicle moves around residential and business neighborhoods collecting the material with the collection bin uncovered, the aerodynamic forces cause the material to become airborne and leave the bin littering the streets. This has a negative impact on several factors associated with the operation not the least of which is public discontent. The project reported here undertakes to address this problem in an experimental investigation using a low speed wind tunnel and appropriately scaled model(s). Flow variables such as velocity and pressure are measured and the dynamics of the problem are analyzed in a systematic manner. Data is generated by employing a two-level factorial experimentation approach. A key requirement for this process to be successful is the availability of a wind tunnel facility that is capable of addressing the engineering tasks outlined for the project. An existing low speed wind tunnel facility at ASU Poly was modified for the purpose of conducting the experimental investigation required. The tunnel modifications included major changes to the inlet section to ensure that the flow entering the test section was well conditioned, a pressure survey setup involving several pressure transducers along with the attendant measurement systems such as a data logger coupled to a desktop computer and a myriad of smaller but essential changes in and around the test section of the tunnel. The modifications were designed, analyzed, fabricated and tested by the graduate student (First Author of the present paper) working on the project. The modification was based on both the short term goal of getting the facility ready for the project at hand and the long term goal of arriving at a configuration, which will enhance the measurements and testing aspects of the engineering technology curriculum being offered in the department. This redesign process will have an immediate impact on the course AET420: Applied Aerodynamics & Wind Tunnel Testing being offered in spring semesters in the department. A wind tunnel design and fabrication process requires the coupling of a few key disciplines in engineering technology. They are aeronautical, mechanical and manufacturing engineering technologies, which form the core focus areas of MMET dept. Some of the changes to the wind tunnel included design of a new inlet convergence, fabrication of this convergence, and subsequent installation. The redesign process was modular which allows additional changes to be made with minimum effort in the future. On the instrumentation front, pressure transducers and a data-logger were fully integrated with the wind tunnel measurement system. Variable inputs were geometric design parameters related to the truck cab and the collection bin sections, wind speed, and yaw angle (cab orientation). Output was dynamic pressure from fifty-four test points in the truck. Statistical analysis of normalized data using Minitab® included analysis of variance, linear regression analysis to establish significant input variables, and contour plots of the pressure fields generated in Excel®. The main effects account for half of the measured response, there are interactions between some main effects, and other probable variables exist. Brief descriptions of the changes to the wind tunnel, design and fabrication of the truck models, factorial design, and the experimental process are given below. As mentioned above, the experimental study described in the present paper supported a M.S. Thesis work in the department. The investigation was comprehensive, rigorous and led to useful results and information that will be of immediate use to the industry at large. Additionally the tasks associated with the study such as the use of rapid prototyping equipment for making the test models will serve as the template for future such endeavors. Even though the redesigned tunnel was used to address the specific problem faced by the industry right now, the students gain valuable experience in solving practical problems of interest to present day industry as they work on a variety of applied projects using the tunnel.