Development of a Rapid Compression and Expansion Machine To Characterize the Ignition Propensity of Multi-Component Liquid Fuels

Combustion has been the primary source for energy production, whether it be from coal, oil, or natural gas, for a very long time. With increasing population and therefore an increased demand for energy, efficiency is becoming a concern. In order to increase efficiency, engines have been downsized and compression ratios have been increased. In doing so, problems have arisen such as knock and low speed pre-ignition. To better understand these problems, an investigation into how fuels ignite at higher pressures is necessary. Real fuels are comprised of multiple components that exhibit significant variations in their own physical and chemical characteristics. Examining these characteristics of real fuels in real world applications has proved to be quite challenging due to the complexity associated with multi-component and multiphase combustion processes. The creation of a novel device to mimic the behavior of reciprocating engines is necessary to gather a fundamental understanding of these fuel properties and their impacts on multiphase combustion processes. The objective of this study is to develop a well-defined experimental platform that can provide high-quality measurements for both gas- and multi-phase ignition processes. Accordingly, a rapid compression expansion machine (RCEM) has been developed and its performance has been comprehensively evaluated. The RCEM is composed of a pneumatically driven actuator, cam, and combustion chamber. The actuator pneumatically pushes a cam that guides the piston to compress the combustion chamber. Pressure time-history profiles have been measured and used to evaluate the compression time for characterizing the polytropic compression behaviors. Considering the relevance to the gasoline fuels, n-Heptane has been used as the primary fuel for this research, which represents the lighter components within an ethanol free fuel. This study summarizes technical challenges in developing a well-defined RCEM, along with experimentally observed ignition behaviors of both gas-phase and multi-phase mixtures

Impact of the Great Recession on Middle Class Americans

This research paper studies the effect of the Great Recession (Late-2000s Recession) on middle-class Americans. It will analyze and cover the extent of the impact through evaluating data on several factors, such as the percent of the middle class in college, percent female participation rate, single parent households (female householder), middle class income, unemployment rate, and several other factors from the years 1970 to 2010. This research will offer insight into the extent of the Great Recession’s impact on the middle-class and identify which key factors had the most significant effect

Development of membranes for hydrogen separation: Pd-coated V-10Pd

Numerous Group IVB and VB alloys were prepared and tested as potential membrane materials but most of these materials were brittle or exhibited cracking during hydrogen exposure. One of the more ductile alloys, V-10Pd (at. %), was fabricated into a thin (107-{micro}m thick) composite membrane coated with 100 nm of Pd on each side. The material was tested for hydrogen permeability, resistance to hydrogen embrittlement, and long term hydrogen flux stability. The hydrogen permeability, {phi}, of the V-10Pd membrane was 3.86 x 10{sup -8} mol H{sub 2} m{sup -1} s{sup -1} Pa{sup -0.5} (avg. of three different samples) at 400 C, which is slightly higher than the permeability of Pd-23Ag at that temperature. A 1400 h hydrogen flux test at 400 C demonstrated that the rate of metallic interdiffusion was slow between the V-10Pd foil and the 100-nm-thick Pd coating on the surface. However, at the end of testing the membrane cracked at 118 C because of hydrogen embrittlement

Modelling distributions of Aedes aegypti and Aedes albopictus using climate, host density and interspecies competition.

Florida faces the challenge of repeated introduction and autochthonous transmission of arboviruses transmitted by Aedes aegypti and Aedes albopictus. Empirically-based predictive models of the spatial distribution of these species would aid surveillance and vector control efforts. To predict the occurrence and abundance of these species, we fit a mixed-effects zero-inflated negative binomial regression to a mosquito surveillance dataset with records from more than 200,000 trap days, representative of 53% of the land area and ranging from 2004 to 2018 in Florida. We found an asymmetrical competitive interaction between adult populations of Aedes aegypti and Aedes albopictus for the sampled sites. Wind speed was negatively associated with the occurrence and abundance of both vectors. Our model predictions show high accuracy (72.9% to 94.5%) in validation tests leaving out a random 10% subset of sites and data since 2017, suggesting a potential for predicting the distribution of the two Aedes vectors

Enhanced hydrogen production from thermochemical processes

To alleviate the pressing problem of greenhouse gas emissions, the development and deployment of sustainable energy technologies is necessary. One potentially viable approach for replacing fossil fuels is the development of a H2 economy. Not only can H2 be used to produce heat and electricity, it is also utilised in ammonia synthesis and hydrocracking. H2 is traditionally generated from thermochemical processes such as steam reforming of hydrocarbons and the water-gas-shift (WGS) reaction. However, these processes suffer from low H2 yields owing to their reversible nature. Removing H2 with membranes and/or extracting CO2 with solid sorbents in situ can overcome these issues by shifting the component equilibrium towards enhanced H2 production via Le Chatelier's principle. This can potentially result in reduced energy consumption, smaller reactor sizes and, therefore, lower capital costs. In light of this, a significant amount of work has been conducted over the past few decades to refine these processes through the development of novel materials and complex models. Here, we critically review the most recent developments in these studies, identify possible research gaps, and offer recommendations for future research