No abstract

Knock remains one of the main limitations for increasing the efficiency in spark-ignition engines. The use of certain alcohol–gasoline blends is an effective way to either mitigate or eliminate knock, allowing the use of higher compression ratios, therefore increasing the efficiency of spark-ignition engines. Methanol and ethanol are alcohols commonly employed for reducing knock, due to their higher octane number and vaporization heat value. Major attention is being paid recently to butanol and its blends with gasoline since they present similar characteristics to gasoline; however, it was found to be the least knock resistant among the three fuels. In the present work, a comparison between the knock performance of methanol–gasoline, ethanol–gasoline and butanol–gasoline blends is carried out, by volume concentrations up to 20 v/v%. This comparison is made in terms of knock intensity and knock probability. Tests are performed in a single-cylinder, variable-compression ratio, Cooperative Fuel Research engine equipped with port fuel injection system, facilitating the comparison against future results obtained by similar experimental facilities. Results obtained allow to reach meaningful conclusions about the capacity of each blend to mitigate knock.

Particulate matter emission from the combustion of fossil fuels is a major concern due to its harmful effects on human health and impact on engine performance. Measurement of the smoke point of these fuels is a key issue in order to assess the tendency of fuels to generate particulate matter. Although certain commercial devices for measuring the smoke point are available, they are very expensive and their precision can still be improved. This paper proposes a novel low-cost device to achieve precise and repetitive smoke point measurements. It is based in an improved image processing algorithm that reduces the measurement error compared to previously developed methods. The device design allows easy adaptation to the smoke point lamp normalized in the American Society for Testing and Materials (ASTM) D1322, without any modification to the lamp.

This paper presents a new assembling for 2 degrees of freedom (DOF) parallel robots for executing rapid pick-and-place operations with low energy consumption, main objectives of pick-and-place operations. A conventional design of 2-DOF parallel robots is based on five-bar mechanisms. Collisions between links are highly possible, restricting the end-effector workspace and/or increasing the trajectory time to avoid collisions. In this work, an alternative assembling for preventing collision is presented. This novel assembling allows exploring the difference between the four five-bar mechanism congurations for the same position of the end-effector. Some of these congurations yield to lower time and/or lower energy consumption for the same motorization. Firstly, a dynamic model of the robot has been developed using Matlab and Simulink and validated by comparison with the results obtained by ADAMS software. A robust cascade PD regulator for controlling joint coordinates has been tuned providing a high accurate end-effector positioning. Finally, simulation results of 4 congurations are presented for executing controlled manoeuvres. The obtained results demonstrate that the conventional conguration is the worst one in terms of trajectory time or energy consumption and, conversely, the best one corresponds to an uncommonly used conguration. A workspace map where all congurations provide faster manoeuvres has been obtained in terms of Jacobian matrix and mechanism elbows distance. The results presented here allow designing a rapid manipulator for pick-and-place operations.

The safety of people working at sea is a subject on which many studies have been carried out. One of the current improvements that has been implemented is the possibility of assigning medical support assistance vessels during specific periods of time, whilst undergoing certain activities or peak seasons in the industry such as fishing seasons. This article proposes an aid system that will support decision making when determining the positioning of such vessels at configurable time intervals, thus shortening the emergency response time. Real data from the vessels, such as coordinates, number of crew, type of fishing gear, etc., are used to carry this out. With the scope of testing the system out, real data from the Spanish fishing fleet in the Bay of Biscay and the medical support assistance vessels available to the Spanish State have been used throughout different seasons. The results obtained convey the “standby” positions for these vessels. The following study of this comparative positioning enables us to calculate the differences between the coordinates calculated by the system and the real positions specified throughout the fishing season. The study also reviews the possibility of improving the emergency response time that would be gained, by increasing the number of medical support assistance vessels for the same area, during the same period.