Free-running Speed Research Articles

Carbon emission due to excess fuel consumption by the trawlers of Thoothukudi, Southeast Coast of India

ABSTRACTSingle-day trawling is commercially practiced along Thoothukudi coast, involving a total of 275 trawlers of varying length range operated from Thoothukudi fishing harbour (8°47’N, 78°9.5’E). The trawlers can be classified in three categories: vessels with overall length (OAL) of 40–50′ (Type 1), OAL 50–60′ (Type 2) and OAL above 60′ (Type 3). Trawlers with OAL of 45′, 55′ and 65′ were selected for the study. Irrespective of the type of vessel, the power required for towing the net was found to be unnecessarily high. The excess power wasted due to faulty trawl designs in Type-1, Type-2 and Type-2 vessels was 55, 87 and 133 hp, respectively. While trawling with optimal trawl design would contribute only 28.67% of the brake horse power (BHP) of the Type 3 vessels, the existing design of trawl used in this type of vessels contributed as much as 50.83% of the BHP. The Type-1, Type-2 and Type-3 trawlers were found to operate with excess fuel consumption at the rate of 103, 212 and 418 L of diesel per cruise, respectively. Based on the annual fuel consumption, true total annual CO2 emission was estimated as 458 tons. The study revealed that the total fuel consumption can be reduced by 40% by optimizing the trawl design and reducing the free-running speed, free-running duration and trawling speed. Further, vessels with an OAL of 60′ and above may be permitted for multi-day fishing in distant waters after suitably limiting the number of fishing trips/month in order to minimize the fuel loss through free running.

Factors Affecting Dental Air-Turbine Handpiece Bearing Failure

SUMMARY Objectives To investigate the influence of various factors on air-turbine handpiece bearing failure through developing standard protocols for testing the bearing longevity. Methods Groups of four air-turbine assemblies (Synea TA-98, W&H, Dentalwerk, Bürmoos, Austria) were subjected repeatedly to a full binary combinatorial set of operating conditions: with and without lubrication, simulated clinical loading, and corrosion protection, all with autoclaving, to the point of failure. A control set was lubricated only. Lubrication (Assistina, W&H), autoclaving (ST-Im30b, Eschmann Bros & Walsh, West Sussex, England), simulated clinical loading (0.56 N at 45° to the turbine axis, after autoclaving), and corrosion protection during autoclaving (magnesium sacrificial anode) were used as required. Free-running speed (Hz) and bearing resistance (μNm) were determined (Darvell-Dyson testing machine) at baseline and after every 10 cycles until turbine failure. Three-way analysis of variance (lubrication × loading × corrosion protection) of log(cycles to failure), with α = 0.05, was used. Results All autoclaved turbines had failed by 560 cycles, while the controls failed at 960-1000 cycles. All three main effects were significant: loading (p<10−6), lubrication (p<0.0002), and corrosion protection (p<0.02), as was the interaction lubrication × loading (p<10−6). No other interaction attained significance. Conclusions Running under load was the most important factor affecting bearing longevity. While autoclaving clearly has a detrimental effect, lubrication effectively increases longevity. A sacrificial anode may be economically worthwhile to extend life further, but low-load usage patterns, as generally instructed, are confirmed as beneficial.

In-process assessment of dental cutting of a leucite-reinforced glass–ceramic

This paper reports an in-process assessment of the dental cutting of a leucite-reinforced glass–ceramic with a high-speed dental handpiece under clinical operating conditions. The dental cutting was performed using a computer-controlled 2-degrees-of-freedom (2-DOF) testing regime and a coarse diamond bur of 106–125 μm grit size. Dynamic forces were monitored during the cutting process using a piezoelectric force dynamometer and a data acquisition system in both time and frequency domains. Bur speeds were found to decrease with the depth of cut and with the feed rate, by a maximum of 10.5% from the free-running speed of 322.2 krpm (1 krpm = 1000 rpm) to 288.4 krpm at the highest feed rate of 60 mm/min and depth of cut of 50 μm. Both the tangential and normal forces increased with the depth of cut and the feed rate, in the ranges of 0.24–1.77 N and 0.60–2.93 N respectively. The torque increased with the depth of cut and feed rate. The specific cutting energy generally decreased with the depth of cut or the feed rate with the exception of a small-scale fluctuation at the higher depth of cut and feed rate. The dental cutting characteristics for the leucite glass–ceramic were similar to those for the feldspathic porcelain but had higher magnitudes.

Torque, power and efficiency characterization of dental air turbine handpieces

Objectives: In a previous paper the flow and free running speed characteristics of dental air turbine handpieces were discussed. The present work was to continue the analysis and characterization of these handpieces by addressing the issues of torque, power generation, efficiency and the specification of figures of merit to aid comparative testing and selection. Methods: Using the principle of the rope brake, torque was determined from stall to free running at a variety of supply pressures for fourteen models of handpiece. Using previous results for air flow rate and free running speed, power and efficiency were calculated. Results: Stall torque was demonstrated to depend on rotor position. Dynamic torque was found to closely approach the expected linear relationship over the range from stall to free running. Several figures of merit (performance indices) were identified which might be used for routine rating and specification of handpieces. Conclusions: Standardized testing can now be performed and effective figures of merit derived to characterize the behaviour of dental air turbine handpieces.

Flow and free running speed characterization of dental air turbine handpieces

Objectives: Dental air turbine handpieces have been widely used in clinical dentistry for over 30 years, yet little work has been reported on their performance. A few studies have been concerned with measurement of speed (i.e. rotation rate), torque and power performance of these devices, but neither investigations of functional relationships between controlling variables nor theory dealing specifically with this class of turbine have been reported. This has hindered the development of satisfactory methods of handpiece specification and of testing dental rotary cutting tools. It was the intention of the present work to remedy that deficiency. Methods: Measurements of pressure, temperature, gas flow rate and rotation rate were made with improved accuracy and precision for 14 ball bearing turbine handpieces on several gases. Functional relationships between gas properties, supply pressure, flow rate, turbine design factors and free running speed were identified and equations describing these aspects of behaviour of this class of turbine developed. Results: The rotor radius, through peripheral Mach number, was found to be a major determinant of speed performance. In addition, gas flow was found to be an important limiting factor through the effect of choke. Conclusions: Each dental handpiece can be treated as a simple orifice of a characteristic cross-sectional area. Free running speed can be explained in terms of gas properties and pressure, with allowance for a design-specific performance coefficient.

Energy consumption of multiple unit cars

In this article are analyzed the effects of increasing the rate of acceleration, free running speed, and rate of braking upon the energy consumption of multiple unit electric passenger cars. Analyses of 4 typical one-mile runs are given.

Energy Consumption of Multiple Unit Cars

In this article are analyzed the effects of increasing the rate of acceleration, free running speed, and rate of braking upon the energy consumption of multiple unit electric passenger cars. Analyses of 4 typical one-mile runs are given.