Contents of Journal of Mechanical Engineering 59, 4 (2008)

ÚRADNÍČEK, J., MUSIL, M.: Study of adaptive control algorithm 
using hysteretic magneto-rheological damper model in 1/4 car 
suspension                                                              175

EL-AWAD, M. M.: A computer-based model for gas-turbine power 
augmentation by inlet-air cooling and water/steam injection             189

BÖSCH, P., SCHAUSBERGER, P., BECKMANN, G., JELEMENSKÝ, K.,
FRIEDL, A.: Example of optimisation and heat integration on 
a basis of ethanol plants                                               205

BENDIGERI, CH., HEGDE, D., BADARI NARAYANA, K., RAMACHANDRA, K.:
Computer modelling of influence actuation and sensing in 
piezoelectric smart materials                                           217

This paper presents a study of the semiactive adaptive control algorithm through numerical simulation where the adaptive control is compared to the widely used skyhook control and passive suspension. A hysteretic magneto-rheological (MR) damper model is developed so that sensitivity of the system variables with respect to the control variable can be evaluated for the purpose of employing the adaptive control algorithm based on the gradient search method. This study includes discussions of the MR damper model setup, a 1/4 car suspension model setup, dynamic analysis approach and tuning of the controllers parameters as well as passive damping. The dynamic analysis is performed in the time domain using sine sweep excitation without the need to linearize such a nonlinear semiactive system. Through simulations, the effectiveness of both controllers and passive suspension is demonstrated for vibration isolation. Effectiveness of all setups under high frequency random excitation for why the suspension is not optimally tuned is demonstrated to study adaptability of the setups under different driving conditions.

The paper presents a computer-based thermodynamic model that estimates the effects of power augmentation methods on the gas turbine power and heat rate. The model takes into consideration the effect of evaporative or refrigerative inlet-air cooling and allows for water or steam injection into the combustion chamber. The formulation of the model improves upon the conventional "standard-air" analysis by including the effects of water on the working-fluid properties, by accounting for the mass of fuel, and by adopting the exact variable specific-heat approach. The model also improves the accuracy and extends the scope of the analysis by solving an energy equation for the combustion process, which enables either the combustion temperature, or the required rate of fuel consumption, to be specified and the other to be calculated. The paper describes the thermodynamic model and the computer program based on it. Verification of the computer-based model against relevant published data is also presented and discussed.

By means of the process simulation tool IPSEPro and pinch analysis, the authors identified and evaluated strategies for energy saving and heat transport in ethanol plants with a production target below 10.000 t/a. It is shown, that with the standard set-up the integration of the basic ethanol plant has little potential for heat integration. By increasing the pressure in a rectification column of the distillation process more transferable energy is available which is followed by a reduction of 27% and 24% in heating and cooling duty of the plant.

To decide whether process steam or hot water is the optimal heat transfer medium for the small-scale ethanol process, the complete heat exchanger network was balanced to both cases. The comparison led to the conclusion, that in this case the heat is best transported by steam. This is due to a higher heat conductivity that concludes in a lower demand for the heat exchangers area for all examined units.

Piezoelectric materials create electrical charge when mechanically stressed and vice versa. In recent years, the range of applications for piezoelectric components has rapidly expanded in various fields. In the present work, experimental studies have been carried out to understand the behaviour of piezoelectric smart material and structure. Also finite element method based on numerical solution has been developed to analyse the deformation, electric potentials and natural frequencies of a piezoelectric smart structure subjected to external mechanical or electrical loadings. We considered eight-node hexahedral element for the analysis. We have developed a code to solve three-dimensional structures integrated with piezoelements using MATLAB software and the performance of the three-dimensional models has been compared with analytical methods for the same configuration. The standard benchmark problems have been considered for solving by presented finite element and analytical methods for the same configurations, and the comparison of results is in good agreement.