Comparing Modes of Transportation with an Improved Karman-Gabrielli Diagram

Abstract

Purpose – To find, how passengers and freight transport efficiency depends on vehicle cruise speed. Based on the Karman-Gabrielli Diagram, four new diagrams are investigated. Plotted is a) the lift-to-drag ratio (weight-to-drag ratio) versus cruise speed. b) Vehicle weight is replaced by the weight of the payload. c) Plotted is the inverse of energy consumption per payload and range versus cruise speed. d) Energy consumption is replaced by primary energy. --- Methodology – For each of the four new diagrams and for each considered means of transport, the governing equations are derived or obtained from literature. Data is collected and the diagrams are plotted. Results are discussed based on new figures of merit visualized in the form of straight iso-lines in the log-log plot. With normal axis the straight lines turn into a typical Pareto fronts. --- Findings – Faster cruise speed of a vehicle is associated with reduced efficiency. More meaningful results are obtained if vehicle weight is replaced by the weight of the payload. Even better, if energy consumption is used or primary energy consumption compared to a slower vehicle. Freight ships are the best in fuel economy. The best compromise between fuel consumption and speed may be achieved by the hyperloop. --- Research Limitation – This paper includes only a selection of vehicles from each category due to limited data accessibility. --- Practical Implications – The Karman-Gabrielli Diagrams enable transportation users to make decisions regarding the most suitable mode of transport, considering various factors such as speed, economy, and environmental impact. --- Originality – This seems to be the first report that extends the Karman-Gabrielli Diagram in such a way and proposes new transport figures of merit.