Macroscopic Parameters of Fuel Sprays Injected in an Optical Reciprocating Single-Cylinder Engine: An Approximation by Means of Visualization with Schlieren Technique.

This paper proposes a sensor system for an internal combustion engine based on a new vision-based algorithm supported by the Schlieren sensorization technique, which allows to acquire the macroscopic parameters of the fuel spray injected in a reciprocating internal combustion engine under unmanned aerial vehicle-like conditions. The sensor system proposed here is able to automatically determine the spray cone angle, its area and its penetration. In addition, the external surface and the volume of the fuel spray is estimated together with the injector opening delay and the ignition delay. The developed algorithm was experimentally tested using a conventional diesel fuel in a single-cylinder engine with an optically adapted head but with easy application and other configurations of reciprocating internal combustion engines. These spray macroscopic parameters allow to analyze, among others, the effect of the spray on the development of both the injection and combustion processes under different operating conditions. The estimation of the external surface of the spray makes it possible to determine the amount of fuel in the spray that is in contact with the surrounding air, with the possibility to link this parameter to the combustion efficiency and emission reduction. Consequently, obtaining the injector opening delay and the ignition delay are important parameters in the combustion phenomenon. In addition, the ignition delay has a great influence on both the engine design and its performance in the study of the air-fuel blending process, in the efficient combustion process and in the reduction of emissions.

Transabdominal ultrasound to assess the displacement of the bladder base during abdominal and pelvic floor contractions in continent parous versus nulliparous women.

INTRODUCTION AND HYPOTHESIS: The effect of different abdominal contractions on the position of pelvic organs in parous women during postpartum exercises has not been sufficiently assessed. The aim of this study was to evaluate the displacement of the bladder base (BB) during different pelvic floor and abdominal contractions in parous women compared to nulliparous women. We hypothesised that abdominal and perineal contractions will produce a disparate effect on the position of the BB between groups. METHODS: Cross-sectional study including a convenience sample of 63 volunteers (35 nulliparous vs. 28 postpartum women). Transabdominal ultrasound was used in mode B to image the displacement of the BB. The protocol included six different pelvic floor and abdominal contractions commonly used in postpartum rehabilitation. RESULTS: The BB elevated significantly more in the postpartum group compared to nulliparous women when performing submaximal contraction of pelvic floor and transversus abdominis muscles simultaneously with axial elongation of the back (0.93 ± 0.55 cm in parous women vs. 0.66 ± 0.46 cm in nulliparous women). In contrast, the BB was found to descend significantly during a curl-up contraction in both groups (0.93 ± 0.55 cm in parous women vs. 0.66 ± 0.46 cm in nulliparous women). CONCLUSIONS: The overall results of this study showed that perineal and superficial abdominal contractions produced different immediate effects compared to deep abdominal contractions on the displacement of BB in parous and nulliparous women. Further research is required to assess the long-term effects of these contractions.

New Sensor Device to Accurately Measure Cable Tension in Cable-Driven Parallel Robots.

Cable-driven parallel robots are a special type of robot in which an end-effector is attached to a fixed frame by means of several cables. The position and orientation of the end-effector can be controlled by controlling the length of the cables. These robots present a wide range of advantages, and the control algorithms required have greater complexity than those in traditional serial robots. Measuring the cable tension is an important task in this type of robot as many control algorithms rely on this information. There are several well-known approaches to measure cable tension in cable robots, where a trade-off between complexity and accuracy is observed. This work presents a new device based on strain gauges to measure cable tension specially designed to be applied in cable-driven parallel robots. This device can be easily mounted on the cable near the fixed frame, allowing the cable length and orientation to change freely, while the measure is taken before the cable passes through the guiding pulleys for improved accuracy. The results obtained from the device show a strong repeatability and linearity of the measures.

SwimOne. New Device for Determining Instantaneous Power and Propulsive Forces in Swimming.

The propulsive forces and instantaneous power that are generated by a swimmer have a great influence on the swimming performance. This works presents a new device, called SwimOne, for measuring propulsive force and estimating the instantaneous power of the swimmer. In addition, the detailed prototype is able to exert a customizable opposition force to the swimmer for training purpose. The conceptual idea is presented by describing the differential equation of the swimmer and the protocol for a factible estimation of the instantaneous power. The variables that are to be measured and estimated are identified and, consequently, the sensor and actuator systems can be selected. The high-level and detailed designs of the prototype are presented together with the protocol that is carried out in order to validate the sensor and actuation systems. The device is able to monitor the variables of interest of the swimmer together with the propulsive force and instant power. Finally, some experiments are carried out providing the results of several participants swimming in crawl, backstroke, butterfly, and breaststroke styles in the presence of different opposition force. The preliminary results show that SwimOne is valid for measuring instantaneous force and power with different loads in swimming.

Novel Methodology for Football Rebound Test Method.

Assessing and keeping control of the mechanical properties of sport surfaces is a relevant task in sports since it enables athletes to train and compete safely and under equal conditions. Currently, different tests are used for assessing athlete- and ball-surface interactions in artificial turf pitches. In order to make these evaluations more agile and accessible for every facility, it is important to develop new apparatus that enable to perform the tests in an easier and quicker way. The existing equipment for determining the vertical ball behavior requires a complex and non-easily transportable device in which the ball must be fixed to the upper part of the frame in a very precise position by means of a magnet. The rebound height is determined by capturing the acoustic signal produced when the ball bounces on the turf. When extended tests are conducted, the time required to evaluate a single field is too high due to the non-valid trials. This work proposes a novel methodology which allows to notoriously decrease the time of testing fields maintaining the repeatability and accuracy of the test method together with a compact device for improving its mobility and transport. Simulations and experiments demonstrates the repeatability and accuracy of the results obtained by the proposed device, which decreases the non-valid trials and notoriously reduces the time for field evaluation.

Spray Momentum Flux Novel Estimation Procedure through the Fuel Rate of Injection Using Hydrogenated Fuels with Single Hole Nozzle Diesel Injector.

Sustainable means of transport require the innovation or development of propulsive systems more respectful of the environment. Despite current criticism, modern compression-ignition engines are efficient alternatives also in light aviation and surveillance drones (such as small helicopters), as means of air transport. Currently, the improvement of the injection, air-fuel mixture formation, and combustion processes using sustainable synthetic fuels, produced from renewable raw materials or by carbon dioxide capture, is a reality. For improving the air-fuel mixture formation inside the combustion chamber, one of the key parameters is knowledge of the spray momentum flux because of its effect on the air entrainement. To measure this parameter is complex. However, the experimental determination of the fuel mass flow rate is a common procedure. The objective of this work is the proposal of a novel but robust methodology for the momentum flux estimation of fuel sprays from measurement of the rate of injection. In this work, single-hole nozzles of 115, 130, and 150 µm in diameter are studied. The implemented methodology is applied to three fuels: a diesel fuel without biodiesel, used as reference, and two sustainable synthetic fuels: a gas to liquid fuel and a hydrotreated vegetable oil. With the fuel injection rates and the simple model proposed, the spray momentum flux is estimated under different operating conditions of a common-rail injection system. The results of the spray momentum flux show a very good precision compared with those experimentally and previously obtained with similar fuels but with multihole nozzle. With the method proposed in this work, an adequate forecast of spray momentum flux is obtained in the case of not having an experimental setup that allows direct measurement of the momentum flux. This study can help investigators for fuel spray modeling with novel and renewable fuels in modern propulsive systems.