Model for sectional leading-edge vortex lift for the prediction of rotating samara seeds performance

ABSTRACTThis article presents a development of a simple analytical aerodynamic model capable of describing the effect of leading-edge vortices (LEVs) on the lift of rotating samara wings. This analytical model is based on the adaptation of Polhamus’ method to develop a sectional two-dimensional lift function, which was implemented in a numerical blade element model (BEM) of a rotating samara blade. Furthermore, wind tunnel experiments were conducted to validate the numerical BEM and to assess the validity of the newly developed analytical lift function. The results showed good agreement between the numerical model and the experimental measurements of rotational speed and rate of descent of the samara wing. The results were also compared with numerical predictions using BEM but adopting different lift coefficient expressions available in literature. This research contributed towards efficient aerodynamic modelling of the lift generated by LEVs on rotating samara wings for performance prediction, which could potentially be used in the design of bio-inspired rotary micro-air vehicles.

An Energy Audit for a Three-Function Hydraulic Control System: A Consideration of Pump Arrangements

When designing a hydraulic circuit, there are a number of ways to power each hydraulic function in the circuit. For instance, a single hydraulic function may be powered by its own dedicated pump; or, a hydraulic function may share a pump with additional functions in the circuit. The design question is this: “What is the optimal arrangement of pumps for a given circuit that will result in the lowest energy consumption and the smallest machine size?” This research documents an example study in which a duty cycle from the typical wheel loader is used to study the five possible pump-combinations that exist for powering the lift, tilt, and steering functions of the machine. It is shown that the lowest efficiency for the machine is observed when all three functions are powered by a single pump, and that a 15% efficiency increase may be realized over the single-pump design by giving each function its own dedicated pump. In order to achieve this efficiency increase, the original single pump is replaced by the following pump combination: 1) a pump 69% the size of the original pump for the Lift function, 2) a pump 86% the size of the original pump for the Tilt function, and 3) a pump 31% the size of the original pump for the Steering function. This solution increases the overall pump volume on the machine by 86%, nearly doubling the pump volume on the machine.

Paper 14: Analysis of Valve Gear Dynamics with a Digital Computer

In this investigation, a pushrod operated valve train is simulated by mathematical models of two, three, four, ten, and fifteen degress of freedom. A number of important features are included in the simulation, such as tappet clearance, linkage separation, valve bounce, and valve spring surge. Solutions of the response to cam lift function under specified running conditions, are obtained by numerical means with a digital computer. These are compared with experimental records of pushrod load and valve displacement on a running engine. The use of similar programs to predict valve gear performance is justified by the excellent agreement obtained.