Continuous Power Consumption Research Articles

Experimental study on gas–liquid–liquid macro-mixing in a stirred tank

In this paper, experimental data on the mixing time of the continuous phase and power consumption of gas–liquid–liquid dispersions in a mechanically agitated baffled tank are presented. The electrical conductivity method is taken for the measurement of mixing time and the shaft-torque method for power consumption measurement. Tap water is used as the continuous phase, and kerosene and air as the dispersed ones. The effects of probe/tracer injection position, agitation speed, type of impeller, clearance of impeller off tank bottom, oil volume fraction, gas holdup and physical properties of the dispersed liquids on the macro-mixing of the gas–liquid–liquid system have been investigated. The phenomenon of gas–liquid–liquid macro-mixing in a stirred tank is largely similar to that of liquid–liquid and gas–liquid stirred tanks. Our experiments indicate that the gas–liquid–liquid macro-mixing can be enhanced at higher gas holdups while damped at low gas holdups. Contrary to gas effect, the dispersed oil phase at low holdups increases the macro-mixing intensity but at higher holdups decreases the macro-mixing intensity of the continuous phase. The experimental results show that axial impellers are more energy efficient for gas–liquid–liquid macro-mixing than radial impellers. A simple correlation is developed for predicting the mixing time in gas–liquid–liquid three-phase systems and satisfactory agreement with experimental data is observed.

Self Powered Non-Dispersive Infra-Red CO2 Gas Sensor

This paper describes a non-dispersive infra-red CO2 gas sensor, incorporating a mid-infra-red solid state light source/ detector combination, tuned to match the spectral absorption characteristic of CO2 gas. Injection moulded optics provide low cost manufacture. Continuous operation power consumption is < 3.5mW and pulsed mode with energy per measurement < 6mJ. Self powered operation using a solar cell is demonstrated together with wireless capability. Performance of two path length variants (20mm and 70mm) is described. The sensor shows invariant temperature output characteristic from -25 to 50°C. Accuracy level is typically ±3% of reading.

Multistage-multiorifice flow fractionation (MS-MOFF): continuous size-based separation of microspheres using multiple series of contraction/expansion microchannels

Previously we introduced a novel hydrodynamic method using a multi-orifice microchannel for size-based particle separation, which is called a multi-orifice flow fractionation (MOFF). The MOFF has several advantages such as continuous, non-intrusive, and minimal power consumption. However, it has a limitation that the recovery yield is relatively low. Although the recovery may be increased by adjusting parameters such as the Reynolds number and central collecting region, poor purity inevitably followed. We newly designed and fabricated a microfluidic channel for multi-stage multi-orifice flow fractionation (MS-MOFF), which is made by combining three multi-orifice segments, and consists of 3 inlets, 3 filters, 3 multi-orifice segments and 5 outlets. The structure and dimensions of the MS-MOFF were determined by the hydrodynamic principles to have constant Reynolds numbers at each multi-orifice segment. Polystyrene microspheres of two different sizes (7 μm and 15 μm) were tested. With this device, we made an attempt to improve recovery and minimize loss of purity by collecting and re-separating non-selected particles of the first separation. The final recovery successfully increased from 73.2% to 88.7% while the final purity slightly decreased from 91.4% to 89.1% (for 15 μm). These values were never achievable with the single-stage MOFF (SS-MOFF) having only one multi-orifice segment in our previous work. The MS-MOFF channel will be useful for clinical applications, such as separation of circulating tumor cells (CTC) or rare cells from human blood samples.

25-kW Three-Phase Unity Power Factor Buck–Boost Rectifier With Wide Input and Output Range for Pulse Load Applications

Pulse loads, like solid-state pulse modulators, generate short pulses with a high peak power that exceeds the average power by 100-1000 times depending on the pulse repetition rate. There, the peak power usually is drawn from an energy buffer such as a capacitor bank. The pulse discharges the energy buffer, and it is fully recharged in the time between the pulses by a power supply, which is usually connected to the mains. Due to the worldwide variation in mains voltages and the desired ability to adapt to the capacitor voltage of the modulator, the power supply has to support a wide input and output voltage range. Additionally, the supply should draw a sinusoidal current from the mains while providing energy to the pulse modulator due to electromagnetic interference regulations. Therefore, a general control concept for pulse load applications, which guarantees continuous power consumption from the mains and power factor correction, is described in this paper. Furthermore, measurements of the control principle, which is independent from the converter topology, are presented for a three-phase buck-boost rectifier.

Feasibility of Inductive Communication Between Millimeter-Sized Wireless Robots

This paper shows the feasibility of inductive data transmission between millimeter-sized (2 times 2 times 1 mm3) swarm robots. To fulfill the size restraints, the coils used for inductive transmission were fabricated by micromachining technologies. Since the induced signal at the receiving coil was very small due to the low coupling coefficient, a high amplification gain of the signal amplifier was necessary. Transmitter and receiver electronics for data transmission were constructed and the quality in data transmission between two 2 times 2 mm2-sized micromachined coils was evaluated. With a continuous power consumption of 270 muW in the transmitter, data transmission was successful without communication error up to a distance of 7 mm, which was considered sufficient to enable 2 times 2 mm2 robots to behave as a swarm within the given operation area.

ELECTROHYDRAULIC SYSTEM FOR HIGH SPEED GAS EXCHANGE VALVE ACTUATION

Diesel engine performance can be improved and emissions reduced by improving the power density and combustion cycle efficiency. It can be done by increasing combustion pressure and engine speed which also necessitates improving the controllability of the engine. One of the key elements in improving overall controllability of the engine is the valvetrain. During recent years various camless valvetrain designs for automotive size engines have been introduced, but in bigger engines camless valve actuation is only applied to low speed two stroke marine diesels. Feasible way to realize camless valve actuation in modern and future medium speed diesels is electrohydraulic valvetrain. It, how ever, has numerous shortcomings and difficulties to overcome.An electrohydraulic valvetrain for experimental engine, having performance characteristics twice the level of current medium speed engines, has been developed. Valvetrain offers significant benefits in comparison to traditional cam actuated valvetrain. Valvetrain is able to operate up to engine speed of 1600 rpm and combustion pressure of 400 bar at speed level twice the tradional cam actuation. Hydraulic peak power of the valvetrain is approx 100 kW and shortest controlled actuation time is approx 6 ms for 18 mm stroke. Main challenges in valvetrain design are are keeping the continuous power consumption at reasonable level, controlling the valve speed, precission of valve timing and dynamics of the system in whole as well as individual components.The paper will introduce the system and component design of the prototype system. System and component performance is discussed on basis of Amesim simulation models. Control system design, realization and valvetrain prototype testing are also discussed.

Adaptive-speed/CAV algorithm in a CD-ROM drive to accomplish high data transfer rate and low power consumption

This paper presents an adaptive-speed/CAV algorithm which regulates the disc velocity in a CD-ROM system to accomplish high data throughput (bit rate) during continuous playback and low power consumption during continuous data access. The adaptive-speed profile is based upon quasi-CLV control which allows drive optimisation towards both data throughput and access time. The presented algorithm can automatically distinguish between two operating modes-continuous access and continuous playback. By detecting the state of continuous access, the CD-ROM drive switches its spindle-motor loop into a constant angular velocity (CAV) mode, avoiding therefore the acceleration/braking of the motor, and thus reducing the power consumption. By detecting the state of continuous playback, the spindle motor will be set to follow an adaptive-speed profile which is highly optimized for data transfer rate. The software and hardware implementation of the CAV/quasi-CLV switching technique in a CD-ROM system is also described.