Optimisation of autoselective plasma regeneration of wall-flow diesel particulate filters

The increase in number of diesel powered vehicles has led to greater concern for the effects of their exhaust emissions. Engine manufacturers must now consider using diesel particulate filters to make their engines meet the legislated limits. Diesel particulate filters can remove more than 95% of the particulates from the exhaust flow but require cleaning, known as regeneration. This thesis describes the research and optimisation of the Autoselective regeneration system for cordierite wall flow diesel particulate filters. The novel Autoselective technology uses an atmospheric pressure glow discharge plasma to selectively oxidise particulate matter (soot) trapped within the filter. The aim of this research was to produce a regeneration system that can operate under all exhaust conditions with a low energy demand and no precious metal dependence to compete with the numerous pre-existing technologies. The effect of discharge electrode type and position on regeneration performance has been investigated in terms of regeneration uniformity, power requirement and regeneration rate. The results showed that the electrode orientation had a large effect on regeneration distribution and energy demand. The electrode capacitance and breakdown voltage was shown to affect the choice of power supply circuit because not all power supply topologies were suitable for powering electrodes with >100 pF capacitance. A number of power supplies were designed and tested, a voltage driven resonant transformer type supply was shown to be optimal when used in conjunction with a swept frequency. The current and frequency ranges of electrical discharges were continuously variable, and their effect on discharge regeneration performance was studied. The results showed that the discharge frequency had no effect on the regeneration process but did affect spatial distribution. An optimised resonant transformer power supply was designed that was ideally suited for the electrodes used. A novel power modulation strategy, which used a switching frequency phase locked to the ~ iii ~ modulating frequency, was employed which extended the operating range of the discharge to below 10 mA for electrode separations > 7.5 mm. The heat flows within the filter and discharge during regeneration were analysed and the filter damage process was linked to the heat released by the discharge inside the filter wall. Other filter materials were compared based on the findings and Mullite ceramic was identified as a potentially better filter material for Autoselective regeneration. The filtration efficiency is important and was observed to be affected by the Autoselective process. The effect of the discharge on filtration efficiency was studied and the mechanism of particulate re-entrainment was identified as a combination of electrostatic and electro-acoustic forces. The Autoselective technology was successfully implemented in both flow-rig and on-engine tests. Results showed significant reduction in back-pressure for power inputs of ~ 500 W. The understanding of the Autoselective regeneration system has been improved and the research resulted in a novel method of filter regeneration

Low power auto selective regeneration of monolithic wall flow diesel particulate filters

This paper presents research into a novel autoselective electric discharge method for regenerating monolithic wall flow diesel particulate filters using low power over the entire range of temperatures and oxygen concentrations experienced within the exhaust systems of modern diesel engines. The ability to regenerate the filter independently of exhaust gas temperature and composition significantly reduces system complexity compared to other systems. In addition, the system does not require catalyst loading and uses only massproduced electronic and electrical components, thus reducing the cost of the after-treatment package. Purpose built exhaust gas simulation test rigs were used to evaluate, develop and optimise the autoselective regeneration system. On-engine testing demonstrated the performance of the autoselective regeneration process under real engine conditions. Typical regeneration performance is presented and discussed with the aid of visual observations, particulate mass measurements, back pressure measurements and energy consumption. The research demonstrates the potential of the novel autoselective method for diesel particulate filter regeneration. The autoselective process does not require an exhaust by-pass and enables the system to be low power, catalyst-free and exhaust temperature independent

SPIRIT checklist.

BackgroundNitrous oxide has shown potentially as an efficacious intervention for treatment-resistant depression, yet there remains insufficient evidence pertaining to repeated administration of nitrous oxide over time and active placebo-controlled studies with optimal blinding. Thus, we aim to examine the feasibility and preliminary efficacy of a six-week follow up study examining the effects of a 4 week course of weekly administered nitrous oxide as compared to the active placebo, midazolam.MethodsIn this randomized, active placebo-controlled, pilot trial, 40 participants with treatment-resistant depression will receive either inhaled nitrous oxide (1 hour at 50% concentration) plus intravenous saline (100mL) or inhaled oxygen (1 hour at 50% concentration) plus intravenous midazolam (0.02 mg/kg in 100mL, up to 2mg) once per week, for 4 consecutive weeks. Participants will be followed up for 6 weeks starting from the first treatment visit. Primary feasibility outcomes include recruitment rate, withdrawal rate, adherence, missing data, and adverse events. The primary exploratory clinical outcome is change in Montgomery-Åsberg Depression Rating Scale (MADRS) score at day 42 of the study. Other exploratory clinical outcomes include remission (defined as MADRS score DiscussionThis pilot study will provide valuable information regarding the feasibility and preliminary efficacy of repeated nitrous oxide administration over time for treatment-resistant depression. If feasible, this study will inform the design of a future definitive trial of nitrous oxide as an efficacious and fast-acting treatment for treatment-resistant depression.Trial registrationClinicalTrials.gov NCT04957368. Registered on July 12, 2021.</div

Schedule of enrolment, interventions, and assessments.

Schedule of enrolment, interventions, and assessments.</p

Study protocol.

BackgroundNitrous oxide has shown potentially as an efficacious intervention for treatment-resistant depression, yet there remains insufficient evidence pertaining to repeated administration of nitrous oxide over time and active placebo-controlled studies with optimal blinding. Thus, we aim to examine the feasibility and preliminary efficacy of a six-week follow up study examining the effects of a 4 week course of weekly administered nitrous oxide as compared to the active placebo, midazolam.MethodsIn this randomized, active placebo-controlled, pilot trial, 40 participants with treatment-resistant depression will receive either inhaled nitrous oxide (1 hour at 50% concentration) plus intravenous saline (100mL) or inhaled oxygen (1 hour at 50% concentration) plus intravenous midazolam (0.02 mg/kg in 100mL, up to 2mg) once per week, for 4 consecutive weeks. Participants will be followed up for 6 weeks starting from the first treatment visit. Primary feasibility outcomes include recruitment rate, withdrawal rate, adherence, missing data, and adverse events. The primary exploratory clinical outcome is change in Montgomery-Åsberg Depression Rating Scale (MADRS) score at day 42 of the study. Other exploratory clinical outcomes include remission (defined as MADRS score DiscussionThis pilot study will provide valuable information regarding the feasibility and preliminary efficacy of repeated nitrous oxide administration over time for treatment-resistant depression. If feasible, this study will inform the design of a future definitive trial of nitrous oxide as an efficacious and fast-acting treatment for treatment-resistant depression.Trial registrationClinicalTrials.gov NCT04957368. Registered on July 12, 2021.</div