Evaluation of a Pneumatic Vest to Treat Symptoms of ARDS Caused by COVID-19

Critical care patients who experience symptoms of acute respiratory distress syndrome are commonly placed on mechanical ventilators to increase the oxygen provided to their pulmonary systems and monitor their condition. With the pulmonary inflammation typically accompanying ARDS, patients can experience lower ventilation-perfusion ratios resulting in lower blood oxygenation. In these cases, patients are typically rotated into a prone position to facilitate improved blood flow to portions of the lung that were not previously participating in the gas exchange process. However, proning a patient increases the risk of complications, requires up to seven hospital staff members to carry out, and does not guarantee an improvement in the patient's condition. The low-cost vest presented here was designed to reproduce the effects of proning while also requiring less hospital staff than the proning process. Additionally, the V/Q Vest helps hospital staff predict whether patients would respond well to a proning treatment. A pilot study was conducted on nine patients with ARDS from Coronavirus disease 2019 (COVID-19). The average increase in oxygenation with the V/Q Vest treatment for all patients was 19.7 ± 38.1%. Six of the nine patients responded positively to the V/Q Vest treatment, exhibiting increased oxygenation. The V/Q Vest also helped hospital staff predict that three of the five patients that were proned would experience an increase in oxygenation. An increase in oxygenation resulting from V/Q Vest treatment exceeded that of the proning treatment in two of these five proned patients.

Modeling and Control of a Hybrid Opposed Piston Engine

This paper presents the modeling and control of an opposed piston (OP) engine in a novel hybrid architecture. The OP engine was selected for this work due to the inherent thermody-namic benefits and the balanced nature of the engine. The typical geartrain required on an OP engine was exchanged for two electric motors, significantly reducing friction and decoupling the crankshafts. By using the motors to control the crankshaft motion profiles, this configuration introduces capabilities to dynamically vary compression ratio, combustion volume, and scavenging dynamics. To realize these opportunities, a model of the system capturing the instantaneous engine dynamics is essential along with methodology to regulate the crankshaft’s rotational dynamics utilizing the electric motors. The modeling presented here couples a 1D model capturing the gas exchange process during scavenging and a 0D model of the crankshaft dynamics and the heat release profile due to combustion. With the use of this model, a linear quadratic controller with reference feedforward was designed to track the crankshaft motion trajectory. Experimental results are used to validate the model and controller performance. These results highlight the sensitivity to model uncertainty at points with high cylinder pressure, leading to large differences in control input near minimum volume. The proposed controller is, however, still able to maintain tracking error for crankshaft position below ± 1 degree.

Control-oriented modeling of the gas exchange process in rebreathing homogeneous charge compression ignition engines

The purpose of this study is to develop a model for the gas exchange process in a rebreathing homogeneous charge compression ignition (HCCI) engine. HCCI engines are attracting significant attention due to their low emissions and high efficiency. To design the control system of an HCCI engine, it is necessary to develop a control-oriented engine model. The developed model lowers its computational load by combining two types of models. The model consists of a discrete model for the exhaust process (the first half of the gas exchange process) and a continuous model with a variable calculation step size for the rebreathing process (the latter half of the gas exchange process). Also, the constructed model maintained its prediction accuracy, as the pressure pulsation in the exhaust port was modeled, and an unsteady flow equation was used. It was confirmed that the model developed for the gas exchange process calculated in about half time of one cycle and reproduced the results of 1D engine simulation software with a maximum error of about 10% in the in-cylinder pressure, temperature, and trapped mass.

Experimental research on scavenging process of opposed-piston two-stroke gasoline engine based on tracer gas method

The scavenging process of two stroke engine includes free exhaust, scavenging, and post intake process, which clears the burned gas in cylinder and suctions the fresh air for next cycle. The gas exchange process of Opposed-Piston Two-Stroke (OP2S) engine with gasoline direct injection (GDI) engine is a uniflow scavenging method between intake port and exhaust port. In order to investigate the characteristics of the gas exchange process in OP2S-GDI engine, a specific tracer gas method (TGM) was developed and the experiments were carried out to analyze the gas exchange performance under different intake and exhaust conditions and opposed-piston movement rule. The results show that gas exchange performance and trapped gas mass are significantly influenced by intake pressure and exhaust pressure. And it has a positive effect on the scavenging efficiency and the trapped air mass. Scavenging efficiency and trapped air mass are almost independent of pressure drop when the delivery ratio exceeds 1.4. Consequently, the delivery ratio ranges from 0.5 to 1.4 is chosen to achieve an optimization of steady running and minimum pump loss. The opposed piston motion phase difference only affects the scavenging timing. Scavenging performance is mainly influenced by scavenging timing and scavenging duration. With the increased phase difference of piston motion, the scavenging efficiency and delivery ratio increased gradually, the trapping efficiency would increase first and decrease then and reaches its maximum at 14°CA.

Test validated 0D/1D engine model of a swinging valve internal combustion engine

In the quest for reaching ever higher power density of IC engines a much simpler solution has been investigated that allows vehicles to reach a comparable power level with cars equipped with turbo charged engines. The new Swinging Valve (SwV) arrangement enables the unhindered gas exchange process through an engine. In this experiment a flow bench was used to examine a normal poppet valve cylinder head and a cylinder head constructed for the same engine but with Swinging Valves. The flow parameters of the original cylinder head were obtained then the SwV head was investigated in the same way. To examine the practical use of a SwV system a 0D/1D engine simulation had been created, first using the engine with conventional cylinder head. That model had been validated with dynamometer tests. After this stage the results of the Swinging Valve flow measurements were fed in the same 0D/1D engine simulation then the results were compared and examined.

Image Based Grading of Emphysema

Emphysema is permanent abnormal enlargement of alveolar walls due to destruction of the alveolar tissues and thereby affecting the gas exchange process of lungs. Grading is usually done to rank the severity of the disease. This paper is a comprehensive review of the imaging based methods used to monitor the emphysema severity. This article aims at the identification of the best imaging method for emphysema grading. Correlation of imaging outcome with pulmonary function parameters is analyzed. Time frame of reviewed articles included is from 2002 to till date. In this review, the classification methods employed for grading emphysema are examined. The best grading method was chosen based on the superior performance obtained in comparison to all the existing work available so far in grading the severity of emphysema. Threedimensional CT densitometry is found to be highly significant with a correlation coefficient of r = 0.97 at significance value, p < 0.001 for the classification of moderate to very severe emphysema as compared to pulmonary function test (PFT). Further research needs to be done to identify methods for evaluating the progress of emphysema during its mild stage.

Fuel-efficient thermal management in diesel engines via valvetrain-enabled cylinder ventilation strategies

Modern diesel engine aftertreatment systems require elevated temperatures for effective reduction of engine-out emissions. Maintaining elevated aftertreatment temperatures in a fuel-efficient manner is a challenge, especially at low-load engine operation where engine-outlet temperatures are low; therefore, higher engine-outlet temperatures are typically achieved via increased fuel consumption. Previous studies have demonstrated that strategies such as cylinder deactivation (method where there is neither valve motion nor fuel injection in a subset of cylinders, thereby isolating the deactivated cylinders from the gas exchange process) and cylinder cutout (method where there is no fuel injection in a subset of cylinders, implemented with high recirculated gas rates) reduce fuel consumption while elevating engine-outlet temperatures, by reducing the overall airflow through the engine. This article introduces and characterizes “non-fired cylinder ventilation” as alternate means to achieve fuel-efficient aftertreatment thermal management, by reduction of overall airflow through the engine. Fuel injection is deactivated from a subset of cylinders during non-fired cylinder ventilation, and the non-firing cylinders participate in the gas exchange process with the same manifold at a time, thereby reducing the intake-to-exhaust manifold gas exchange through the cylinders. It is demonstrated that non-fired cylinder ventilation shows similar fuel efficiency and thermal management as cylinder deactivation when the valves of the non-firing ventilated cylinders are open by at least 4 mm, due to similar, negligible, gas-exchange losses, while non-fired cylinder ventilation with lower valve lifts enables elevated engine-outlet temperatures with relatively higher fuel consumption than cylinder deactivation. Non-fired cylinder ventilation strategies demonstrate 75 °C higher temperatures at fuel-neutral conditions, and up to 35% fuel savings at similar temperatures, compared to six-cylinder operation.

Development and experimental validation of a real-time capable field programmable gate array–based gas exchange model for negative valve overlap

Homogeneous charge compression ignition has the potential to significantly reduce NO x emissions, while maintaining a high fuel efficiency. Homogeneous charge compression ignition is characterized by compression-induced autoignition of a lean homogeneous air–fuel mixture. Combustion timing is highly dependent on the in-cylinder state including pressure, temperature and trapped mass. To control homogeneous charge compression ignition combustion, it is necessary to have an accurate representation of the gas exchange process. Currently, microprocessor-based engine control units require that the gas exchange process is linearized around a desired operating point to simplify the model for real-time implementation. This reduces the models’ ability to handle disturbances and limits the flexibility of the model. However, using a field programmable gate array, a detailed simulation of the physical gas exchange process can be implemented in real time. This paper outlines the process of converting physical governing equations to an offline zero-dimensional gas exchange model. The process used to convert this model to a field programmable gate array capable model is described. This model is experimentally validated using a single cylinder research engine with electromagnetic valves to record real-time field programmable gate array gas exchange results and comparing to the offline zero-dimensional physical model. The field programmable gate array model is able to accurately calculate the cylinder temperature and cylinder mass at 0.1 °CA intervals during the gas exchange process for a range of negative valve overlaps, boost conditions and engine speeds making the model useful for future real-time control applications.