New Flyer Industries Bus Door Air Curtain Design and Analysis

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Ahmed, Ashir
Bhudia, Deepak
Crew, Stephen
Zonneveld, Jack
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This project explores the design and analysis of an air curtain to be used in New Flyer’s electric bus. New Flyer is a leading bus manufacturer in North America and is working towards increasing the efficiency of the Xcelsior Charge line of electric buses. New Flyer identified the door as a major energy loss source during passenger ingress and egress. An air curtain is proposed in the report to reduce energy loss through the door. The proposed design forms an air boundary separating the outside atmosphere from the bus cabin atmosphere to reduce heat transfer through the door boundary when the doors are open. The team had the task to develop a solution to reduce heat transfer through the door. The design is required to meet industry standards outlined by the American Public Transport Agency (APTA) and the Americans with Disabilities Act (ADA). Although no specific project budget was set, cost was minimized where possible and influenced design decisions. The final design was to be submitted to the client as a CAD model along with the results of the analysis obtained. The submission to the client also included Failure Modes and Effects Analysis (FMEA) for designing, manufacturing, and installation of the air curtain. In addition, future recommendations concerning both the design and analysis are included in the report. STAR-CCM+ was utilized to perform a Computational Fluid Dynamic (CFD) analysis of the air curtain design. Initial analysis of the air curtain did not show promising results, and hence, three more studies were performed to explore the air curtain performance. Simulation data showed increased heat transfer rates for the door equipped with the air curtain; however, it was demonstrated that the air curtain was successful in creating a barrier to separate internal and external air. Due to the lack of HVAC return in the simplified CFD model, the air leaving the air curtain plenum was exiting the bus at an increasing rate. With optimization of the HVAC return, nozzle position, angle, and cross-sectional area, the observed rate of heat transfer through the door would improve. This report includes the steps taken to design and perform CFD analysis on the air curtain, along with the challenges encountered by the team. Additionally, base case CFD analysis (without the air curtain) was performed to compare the results with the air curtain analysis to help understand the value added. The final design proposed to the client is a dual-fan-operated air curtain. Centrifugal fans used in the air curtain are operated using 24VDC with a power rating of 175.2W each to produce 2200 CFM combined. A distinct feature of the design is its compact geometry which takes up less space and requires fewer changes to the baseplate. The geometry design quickly spreads the flow along the length of the door as the fans are activated to form an air door when the bus door is opened. High-density polyethylene (HDPE) used for the design makes it highly impact-resistant, allowing it to meet the durability requirements for the transit bus application. The energy consumption of the fans used is 0.741 kWh for one day of operation, which is significantly lower than the average energy consumption by the HVAC system used to heat and cool the bus with an average daily consumption of 70.57 kWh in Winnipeg. The total cost for producing a prototype for testing is approximately $4480, which includes the adjustments to the CAD modeling, rework instruction for the prototype air curtain, rapid prototyping, and installation covering both mechanical and electrical work involved. The cost rises up to $16000 for a detailed production-ready design for implementation in the bus.
Mechanical Engineering