Contact Force Measurements in Cam and Follower Lubricated Contacts

Cam-follower contacts are characterized by continuous changes of operating parameters such as speed, load and geometry, so that both numerical simulations and experimental measurements are very complex. An experimental apparatus has been specifically designed and realized to perform tests with cam–follower pairs. The apparatus allows measurements of contact forces with a custom-made dynamometer and of lubricant film thickness and shape with optical interferometry. After an introductory review of experimental works on cam-follower pairs mainly related to force measurements, the test rig used for the experimental work reported in the paper is briefly described. Some trends of all components of the contact forces measured during the rotation of a circular eccentric cam and an engine spline cam are presented. Tests have been performed at different rotational speeds and preloads. The friction trends can be associated to mixed and boundary lubrication regimes. Some unattended friction peaks are found in tests with the spline cam and possible explanations are given

Enhanced Current-Type P-HIL Interface Algorithm for Smart Transformers Testing

The energy systems are evolving towards the wide integration of power electronics-based technologies, such as electric vehicles. A promising solution to increase the grid controllability is represented by grid-forming converters, such as smart transformers (STs). Being a new technology, the ST experimental testing is a fundamental step before commercialization. Instead of performing time consuming and not flexible on-field tests, the Power Hardware In the Loop (P-HIL) offers a flexible testing environment for experimentally validating new technologies. The real-time simulation of the electrical grid offers the possibility to vary quickly the testing environment, while the power amplification stage offers the validation of the real hardware. Despite the clear testing advantages, the P-HIL stability and testing accuracy is still a matter of study. This paper introduces a new P-HIL interface approach for ST application, that can guarantee high testing accuracy in a large frequency spectrum. The proposed approach combines the tracking capability of the existing controlled Current-Type P-HIL interface algorithm, with the well-known Partial Circuit Duplication approach. The accuracy and stability analysis has been performed analytically and validated by means of extensive experimental P-HIL testing

Sviluppo di un framework di algoritmi per l'analisi del segnale di pressione nel cilindro

Descrizione di una serie di algoritmi, realizzati nel linguaggio di programmazione Python, atti all'analisi di dati provenienti dall'analisi al banco di motori a combustione interna; richiami dei principali parametri calcolati negli algoritmi e descrizione del linguaggio di programmazione

546 Meat quality of Suffolk and Bergamasca lambs slaughtered at 90 days of age

Twenty lambs, 10 Suffolk (S) e 10 Bergamasca (B) born from single (SI) and twin type of birth (TW), were employed. Lambs fed the same diet. Chemical-physical analysis were performed on raw Longissimus lumborum (LL). B showed the lowest cooked loss on cooked LL, the highest value of a* and b* on raw meat. As regard fatty acid composition, LL of B showed the highest saturated fatty acids and the lowest value of polyunsaturated acids. Twin subjects showed raw meat with the lowest value of ether extract and with a healthy fatty acid composition

Synchronization of Low Voltage Grids Fed by Smart and Conventional Transformers

The Smart Transformer (ST) is a power electronicsbased transformer, which operates as grid-forming converter in the low voltage-fed grid. It synthesizes the voltage waveform with magnitude, phase and frequency independently from the main power system. If a meshed operation of the ST with a conventional transformer is required, to improve the power flow control and to control the voltage profile, the voltage waveforms between the two grids have to be synchronized. The switching under different voltage magnitude, phase or frequency, can lead to a large power in-rush. This work proposes a synchronization strategy that enables a seamless transition of the ST to parallel operations with conventional transformers. Differently from classical communication-based methods, this work addresses a more realistic implementation case with limited communication infrastructure. The ST relies only on local measurements and on its advanced control capability to determine the effective switch to parallel operations. The performance of the proposed strategy has been proved analytically and through simulations in a PLECS/Matlab environment, and validated experimentally by means of Power-Hardware-In-Loop (PHIL) evaluation

Voltage-Dependent Load Levelling Approach by means of Electric Vehicle Fast Charging Stations

Intermittent generation and load demand are one of the major challenges for grid operators. Caused for example by renewables power variability or electric vehicle charging, it can create mismatches between the realtime and forecasted demand, affecting frequency regulation. To alleviate this mismatch, operators have to resort either on the balancing market or on extensive use of energy storage systems, which increases operation costs. This paper introduces a load levelling approach exploiting the voltage dependency of the loads. With a controlled reactive power injection, the converters of fast charging stations can influence the voltage profile, and consequently the power consumption of voltage-dependent loads. The approach has two main goals: minimizing the mismatches with respect to the demand forecast and reducing the grid losses. Fast charging stations are particularly suited for this approach. Being employed with full capacity for charging only for short-time, their spare capacity can be exploited to apply the load levelling approach. This proposed approach is discussed theoretically and analyzed in a modified distribution network in Northern Germany. Parameters variation analysis has been performed to thoroughly demonstrate the effectiveness of the approach under different load/grid conditions. Its feasibility has been evaluated by means of power-hardware-in-the-loop tests