Exposure of thermoplastics to methanol–gasoline blends: A material compatibility study

Alcohols are increasingly being looked upon as the most viable alternative to the conventional sources of energy. Methanol is the first member of the alcohol family and can be easily synthesized from syngas. It is an attractive blend to gasoline due to its advantageous properties. There is a necessity to make sure that the infrastructure is ready to adapt these alternative fuels. Hence, the aim of this study is to assess the degradation of widely used thermoplastics in fuel tanks, pipes, and the fuel injection system, namely, polytetrafluoroethylene (PTFE), polyethyleneterephthalate (PET), and high density polyethylene (HDPE) post exposure to methanol–gasoline blends (P100, M15, and M30) for a period of 4, 10, and 30 days. The effects of the exposure were examined by comparing changes in gain/loss of mass, hardness, elongation, and tensile strength. The surface morphology changes of the polymeric coupons were characterized by scanning electron microscopy and their elemental analysis was done by energy dispersive X-ray spectroscopy. The studied materials were found to gain mass in the order HDPE > PTFE >PET. The decrease in hardness was found to be more in HDPE followed by PTFE and PET. PTFE and PET showed reduction in strength but an increase in tensile strength was observed for HDPE post exposure to fuel blend. Highest change in elongation was found in HDPE followed by PTFE and PET. The changes were found to be the least in P100 followed by M15 and maximum in M30 blends for all immersion periods.

Economic Evaluation of an Ammonia-Fueled Ammonia Carrier Depending on Methods of Ammonia Fuel Storage

This study proposed two concepts for ammonia fuel storage for an ammonia-fueled ammonia carrier and evaluated these concepts in terms of economics. The first concept was to use ammonia in the cargo tank as fuel and the second concept was to install an additional independent fuel tank in the vessel. When more fuel tanks were installed, there was no cargo loss. However, there were extra costs for fuel tanks. The target ship was an 84,000 m3 ammonia carrier (very large gas carrier, VLGC). It traveled from Kuwait to South Korea. The capacity of fuel tanks was 4170 m3, which is the required amount for the round trip. This study conducted an economic evaluation to compare the two proposed concepts. Profits were estimated based on sales and life cycle cost (LCC). Results showed that sales were USD 1223 million for the first concept and USD 1287 million for the second concept. Profits for the first and second concepts were USD 684.3 million and USD 739.5 million, respectively. The second concept showed a USD 53.1 million higher profit than the first concept. This means that the second concept, which installed additional independent fuel tanks was better than the first concept in terms of economics. Sensitivity analysis was performed to investigate the influence of given parameters on the results. When the ammonia fuel price was changed by ±25%, there was a 15% change in the profits and if the ammonia (transport) fee was changed by ±25%, there was a 45% change in the profits. The ammonia fuel price and ammonia (cargo) transport fee had a substantial influence on the business of ammonia carriers.

Hydrostatic pressure loads for a tank using “CID Distributed Loads” fields in a PATRAN FEM model

The purpose of this paper is to present a practical way to introduce distributed loads on the walls of a tank in order to perform a FEM analysis using PATRAN/NASTRAN programs. The problem is generated mainly by the fact that there are gravitational accelerations in the three directions of the moving airplane that produce a great number of combinations of inertial loads and consequently a great number of critical load cases. We compared the performed stress analysis with the loads obtained with this method in different cases for 𝑛𝑛=1. (Different forms of the fuel tanks and different placements of the tank inside the aircraft). The form and the density of the grid do not significantly affect the precision of the real inertia loads. Using the presented method one can reduce the volume of FEM files used in the analysis and can quite accurately reproduce the pressure loads on the fuel of a moving aircraft.

Analysis Methodology of Unusable Fuel Supply for Large Rotorcraft Airworthiness Certificate

The unusable fuel quantity plays a key basis for calibration of aircraft fuel gauge and fuel measurement system. Using large helicopter fuel tanks as case study, the paper described airworthiness requirements for fuel system design and current research development. In particular, the paper presented an analysis method can be utilized and referenced as means of compliance for airworthiness requirements. This method will reduce the qualification time and save money for physical and dynamic bench test/flight test in the future.

Design of Fuel Supply Curves for Aircraft Center of Gravity Balance Based on DCT Compression

The center of gravity (CG) has a significant influence on the controllability, stability, and fuel efficiency of the aircraft. For the aircraft with multiple fuel tanks, the CG position can be controlled by the fuel quality of different fuel tanks during flight. In this paper, an optimization method based on discrete cosine transform (DCT) compression is proposed to solve the optimization strategy of aircraft multi-tank fuel supply according to the current aircraft mission and engine working requirements. The transform coefficients of the low frequency components are used as design variables to represent the fuel supply curves. The improved KS function is proposed to deal with constraints. The numerical example is demonstrated to verify the effectiveness of the proposed method.

Deep (Meta)genomics and (Meta)transcriptome Analyses of Fungal and Bacteria Consortia From Aircraft Tanks and Kerosene Identify Key Genes in Fuel and Tank Corrosion

Microbial contamination of fuels, associated with a wide variety of bacteria and fungi, leads to decreased product quality and can compromise equipment performance by biofouling or microbiologically influenced corrosion. Detection and quantification of microorganisms are critical in monitoring fuel systems for an early detection of microbial contaminations. To address these challenges, we have analyzed six metagenomes, one transcriptome, and more than 1,200 fluid and swab samples taken from fuel tanks or kerosene. Our deep metagenome sequencing and binning approaches in combination with RNA-seq data and qPCR methods implied a metabolic symbiosis between fungi and bacteria. The most abundant bacteria were affiliated with α-, β-, and γ-Proteobacteria and the filamentous fungi Amorphotheca. We identified a high number of genes, which are related to kerosene degradation and biofilm formation. Surprisingly, a large number of genes coded enzymes involved in polymer degradation and potential bio-corrosion processes. Thereby, the transcriptionally most active microorganisms were affiliated with the genera Methylobacteria, Pseudomonas, Kocuria, Amorpotheka, Aspergillus, Fusarium, and Penicillium. Many not yet cultured bacteria and fungi appeared to contribute to the biofilm transcriptional activities. The largest numbers of transcripts were observed for dehydrogenase, oxygenase, and exopolysaccharide production, attachment and pili/flagella-associated proteins, efflux pumps, and secretion systems as well as lipase and esterase activity.