Review of Recent Developments in Wave Rotor Combustion Technology

For some decades, efforts have been made to exploit nonsteady combustion and gas dynamic phenomenon. The theoretical potential of nonsteady-flowmachines has led to the investigation of various oscillatory flowdevices such as pulse detonation engines, wave rotors, pulse jets, and nonsteady ejectors. This paper aims to provide a progress review of past and current research in developing a particular combustion concept: the wave rotor combustor. This pressure-gain combustor appears to have considerable potential to enhance the performance and operating characteristics of gas turbine and jet engines. After attempts in the mid-twentieth century were thwarted by mechanical problems and technical challenges identified herein, recent successes in Switzerland and efforts in the United States benefited from design expertise developed with pressure-exchange wave rotors. The history, potential benefits, past setbacks, and existing challenges and obstacles in developing these nonsteady combustors are reviewed. This review focuses on recent efforts that seek to improve the performance and costs of future propulsion and powergeneration systems

Palladium Nanoparticles Supported on Ce-Metal–Organic Framework for Efficient CO Oxidation and Low-Temperature CO2 Capture

In this article, we report the lowest-temperature CO oxidation catalyst supported on metal–organic frameworks (MOFs). We have developed a facile, general, and effective approach based on microwave irradiation for the incorporation of Pd nanoparticle catalyst within Ce-MOF. The resulting Pd/Ce-MOF material is a unique catalyst that is capable of CO oxidation at modest temperatures and also of efficient uptake of the product CO2 gas at low temperatures. The observed catalytic activity of this material toward CO oxidation is significantly higher than those of other reported metal nanoparticles supported on MOFs. The high activity of the Pd/Ce-MOF catalyst is due to the presence of Ce(III) and Ce(IV) ions within the metal–organic framework support. The Pd nanoparticles supported on the Ce-MOF store oxygen in the form of a thin palladium oxide layer at the particle–support interface, in addition to the oxygen stored on the Ce(III)/Ce(IV) centers. Oxygen from these reservoirs can be released during CO oxidation at 373 K. At lower temperatures (273 K), the Pd/Ce-MOF has a significant CO2 uptake of 3.5 mmol/g

A Review of Wave Rotor Technology and Its Applications

The objective of this paper is to provide a succinct review of past and current research in developing wave rotor technology. This technology has shown unique capabilities to enhance the performance and operating characteristics of a variety of engines and machinery utilizing thermodynamic cycles. Although there have been a variety of applications in the past, this technology is not yet widely used and is barely known to engineers. Here, an attempt is made to summarize both the previously reported work in the literature and ongoing efforts around the world. The paper covers a wide range of wave rotor applications including the early attempts to use wave rotors, its successful commercialization as superchargers for car engines, research on gas turbine topping, and other developments. The review also pays close attention to more recent efforts: utilization of such devices in pressure-gain combustors, ultra-micro gas turbines, and water refrigeration systems, highlighting possible further efforts on this topic. Observations and lessons learnt from experimental studies, numerical simulations, analytical approaches, and other design and analysis tools are presented

Performance Enhancement of Microturbine Engines Topped With Wave Rotors

Significant performance enhancement of microturbines is predicted by implementing various wave-rotor-topping cycles. Five different advantageous cases are considered for implementation of a four-port wave rotor into two given baseline engines. In these thermodynamic analyses, the compressor and turbine pressure ratios and the turbine inlet temperatures are varied, according to the anticipated design objectives of the cases. Advantages and disadvantages are discussed. Comparison between the theoretic performance of wave-rotor-topped and baseline engines shows a performance enhancement up to 34%. General design maps are generated for the small gas turbines, showing the design space and optima for baseline and topped engines. Also, the impact of ambient temperature on the performance of both baseline and topped engines is investigated. It is shown that the wave-rotor-topped engines are less prone to performance degradation under hot-weather conditions than the baseline engines

Leakage Assessment of Pressure-Exchange Wave Rotors

Control of leakage within wave rotors is recognized as a key requirement for efficient operation. Previous studies suggest that experimentally observed performance degradation is substantially due to flow leakage. This work presents a leakage model for predicting leakage-attributed performance degradation of four-port pressure-exchange wave rotors more accurately than previous single-cavity leakage models. The methodology comprehensively considers the leakage paths of the entire device. It combines a wave-rotor quasi-one-dimensional computational fluid dynamics prediction code, experimentally validated for internal gas dynamics with the generalized flow-circuit-modeling capability of a leakage-flow network solver. The computational fluid dynamics program and the network solver step through a series of iterations by sharing common leakage information. Application to a well-instrumented wave-rotor rig is briefly summarized, providing important guidance for the improvement of leakage and performance. The new approach is anticipated to be useful in enhancing the design, operation, and efficiency of a broad class of wave rotors by better understanding leakage and hence designing sealing features to control leakage flows

Efficacy of biorational insecticides against Dubas bug, Ommatissus lybicus (Hem.: Tropiduchidae) in a date palm orchard and evaluation of kaolin and mineral oil in the laboratory

In this study, mineral oil and kaolin as alternatives to conventional pesticide (diazinon) were evaluated to manage Dubas bug, Ommatissus lybicus de Bergevin, in the field and laboratory. In the field experiment, effect of four treatments was evaluated against population density (first and second nymphal stages) and honeydew production (as main damage) of Dubas bug. A single application of each product was applied at the recommended rates. Results showed that kaolin, mineral oil and diazinon were statistically similar in decreasing the population density and damage of Dubas bug. This result makes kaolin and mineral oil as potential alternatives to conventional insecticides in date palm orchards. In the laboratory, mineral oil was effective on egg mortality. In settling choice test, the ability of Dubas bug to discriminate between kaolin-treated and kaolin-untreated leaflets increased significantly over the time and females laid more eggs on untreated leaflets than kaolin-treated leaflets. Results of no-choice test revealed that the leafhoppers could lay eggs on treated leaflets as many as on untreated leaflets

Comparison of the efficacy of a neutral wrist splint and wrist splint with lumbrical unit for the treatment of patients with carpal tunnel syndrome

Purpose: The purpose of this study was to compare the effect of a neutral wrist splint or a wrist splint with an additional metacarpophalangeal (MCP) unit on pain, function, grip and pinch strength in patients with mild-to-moderate carpal tunnel syndrome (CTS). Methods: Twenty four patients received conservative treatment using either the neutral wrist splint or wrist splint with the MCP unit for a period of 6 weeks. Primary outcome measures were pain, function, grip and pinch strength. Data was collected immediately before and after using the two types of splints at baseline (0 weeks) and 6 weeks. Statistical analysis was performed using the paired t-test and independent T-test. Results: Compared to baseline, both the neutral wrist splint and the wrist splint with an MCP unit significantly decreased pain, increased function and pinch and grip strength. Comparisons of the two types of splints for grip (P =0.675) and pinch strength (P =0.650) revealed that there were no significant differences between the two after 6 weeks of wear. However, there were significant differences in pain levels (P =0.022) and the DASH score (P =0.027) between the two types of splints from baseline to 6 weeks. Conclusion: The wrist splint with an MCP unit was more effective than the neutral wrist splint in pain reduction and improvement of function