No abstract

The rotating equipment is a crucial part of system performance reliability. Vibration, as a characteristic of an oscillating body, is a fundamental parameter to determine the dynamic behaviour of the rotor system. The dynamic characteristics include natural frequency, critical speed, mode shape, and vibration response. This paper discussed the application of rotordynamics analysis as a tool to numerically predict the dynamic behaviour of a rotor system. The aim is to determine a rotor system's natural frequency and critical speed by a finite element analysis (FEA) program. The selected method is validated using various analytical methods from other references with small discrepancies in the result. The calculation of FEA using the computational program; they applied the developed program to describe the dynamic characteristic of single and multi-disk rotors. The developed works provided comprehensive results about a rotor system's natural frequency, mode shape, and critical speed and predicted the vibration response due to unbalance. However, other types of rotors, such as coaxial dual rotors, can be further investigated to make the program capable of the general purpose of the rotor. Validation with the real case problem could be an interesting investigation to satisfy the result of developed works.

Compared to traditional lignocellulose biomass, microalgae contain little or no lignin. Traditionally, bioethanol production from microalgae undergoes three major steps: (i) pretreatment; (ii) polysaccharides hydrolysis into simple sugars; and (iii) sugar conversion into bioethanol by fermentation. Microalgae convert sunlight, water, and CO2 into algal biomass. Diatoms, green algae, bluegreen algae, and golden algae are four main classes of microalgae, whereas the two main species of algae are filamentous and phytoplankton algae. Microalgae convert solar energy efficiently, producing an enormous number of various metabolites. Many studies have been conducted to convert microalgae into various biofuels, such as biodiesel, bioethanol, biohydrogen, and biogas. However, compared to biodiesel, bioethanol production from algae throughfermentation consumes less energy with its simplified process. Considering these advantages, a number of potential applications for microalgae have been proposed and developed. Despite the promising of bioethanol from microalgae, it still has a number of obstacles, such as the low fermentable carbohydrate content of microalgae. This article intends to discuss the methods to increase microalgae carbohydrates thoroughly. To solve this problem, several nutritional starvations/limitations, like nitrogen and phosphorous starvation, are currently being considered in this paper.