Stop-start Operation Research Articles

Experimental studies of the air hybrid engine charging operation

Over the last few years, theoretical and modelling studies have been carried out on the feasibility and potential of novel mild air hybrid engine concepts based on production components. These mild air hybrid concepts are able to convert vehicle brake energy into pneumatic energy in the form of compressed air stored in the air tank. The compressed air can then be used to crank-start the engine by either injecting and expanding in the cylinder or driving a production air starter. Thus, the regenerative stop–start operation can be readily realised for improved fuel economy. In order to demonstrate air hybrid engine charging operation experimentally and validate the theoretical analysis, a single-cylinder engine has been adapted to operate in the compressor mode with the novel one-way intake system. Two air intake designs were implemented and tested so that their ability to capture compressed air could be analysed. In particular, it is shown that the compressor mode can be accomplished effectively through a simple cam profile switching device which has been used in production engines. Furthermore, the experimental and analytical results show a good agreement which gives high confidence to the theoretical analyses carried out on different mild air hybrid engine concepts examined.

Start-up of a UASB effluent treatment plant on distillery wastewater

Distillery effluent is a contaminated stream with COD values of up to 30 000 mg/l and low pH values of between 3 and 4. The anaerobic biological treatment of distillery effluents is widely applied as an effective step in removing more than 90% of the COD in the effluent stream. This paper reports on the seasonal operation of a UASB treatment plant treating a distillery wastewater stream with particular focus on seasonal start-up conditions after the first process commissioning. The start-up period was typically one week before process stability could be achieved. It is recommended that the loading rate to the plant be controlled between 4 and 8 kg COD/m3·d until the process is stable and COD removal efficiencies remain, on average, higher than 90%. After the start-up period the loading rate applied (4 to 18 kg COD/m3d) did not significantly affect the COD removal efficiency of the plant. High removal efficiencies of higher than 90% were achieved and stop-start operation of the UASB process posed no problem for treatment. WaterSA Vol.28(1) 2002: 63-68

Simulation and optimisation of intermittent membrane microfiltration

Cyclical stop-start operation as a method of increasing permeate production and lowering energy requirements is discussed. It is thought that the removal of the applied pressure allows the reversible fouling, such as concentration polarisation, to dissipate. A model to simulate intermittent operation is developed and optimised with respect to optimising the permeate production. The model was used to simulate a theoretical optimised run and the results compared to those obtained from experiment. The experiments were performed with a dilute suspension of magnesium hydroxide and a range of cross-flow velocities. The experimental results were in good agreement with those calculated from the theoretical model. The use of intermittent operation showed permeate production increases in the order of 200% when compared to the permeate production of a steady flow run. Energy savings of more than 50% are also reported when using intermittent operation.

Optimisation of intermittently operated microfiltration processes

The intermittent initial period of crossflow microfiltration has been studied, and the nature of foulinglayer deposits ascertained by simple physical inspection. At low crossflow velocity, a visible solid deposit was formed on the inside of the tubular membrane, but at high velocities no such layer could be detected. In this regime, fouling was controlled by the concentration polarisation phenomenon. The initial flux in these cases was restored by stopping the apparatus for a few seconds. Cyclical stop-start operation as a way of increasing permeate production is discussed.

縦方向すみ肉溶接継手の疲労強度 溶接棒継ぎの影響

The purpose of this study is to make clear the influence of the weld surface irregularity induced by the weld stop-start operation on the fatigue strength of longitudinal fillet welded joint. The materials used are 500 MPa and 600 MPa class steels. Weldings are done by manual arc processes and weld stop-start operations are carried out as leaving or filling the crater. The specimen is a flat plate with 16 mm thick and 60 mm wide. After the weld surface irregularities are measured, the specimens are tested under axial cyclic loadings. Then, the fatigue crack initiation and propagation behavior is closely observed. The test results indicate that the weld stop-start operation as filling the crater is preferable with respect to the fatigue strength.

Non-Steady State Thermal Performance of Electrical Machines

Because the ratings of electrical machines continue to increase, there is a growing need to be able to predict their thermal performance under the transient conditions caused by overloading or stop-start operation. The design of electrical machines is often too complex to make an analytic solution feasible, but a general numerical method has been developed to predict component temperatures at the drawing-board stage. The problem to be solved is represented by a thermal resistance-capacitance network, the resulting set of simultaneous equations being solved by a digital computer employing a step-by-step procedure. The number of network nodal points at which the temperature can be calculated is at present restricted by computer storage space to 150, therefore the fully three-dimensional problems which can be solved are of limited complexity. However, the majority of electrical machines can be simplified by assuming axial symmetry, which permits a large variety of problems to fall within the capabilities of this technique.

A Continuous-Loop Magnetic-Tape Magazine and its Applications

Design and operation of an endless-loop <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\frac{1}{4}$</tex> -in. magnetic-tape magazine with uniform low-friction tape motion and a five-channel selective program repeater are described. Features include high-speed solenoid actuation for instantaneously cued stop-start operation, and transistorized audio and control circuitry. Applications are discussed.