Design and development of mild combustion burner

This paper discussed the design and development of the Moderate and Intense Low oxygen Dilution (MILD) combustion burner using Computational Fluid Dynamics (CFD) simulations. The CFD commercial package was used to simulate preliminary designs for the burner before the final design was sent to workshop for the fabrication. The burner is required to be a non-premixed and open burner. To capture and use the exhaust gas, the burner was enclosed within a large circular shaped wall with an opening at the top. An external EGR pipe was used to transport the exhaust gas which was mixed with the fresh oxidant. To control the EGR and exhaust flow, butterfly valves were installed at the top opening as a damper to close the exhaust gas flow at the certain ratio for EGR and exhaust out to atmosphere. High temperature fused silica glass windows were installed to view and capture images of the flame and analyse the flame propagation. The burner simulation shows that MILD combustion was achieved for the oxygen mole fraction between 3-13%. The final design of the burner was fabricated and ready for the experimental validation

Experimental and numerical investigation of spray characteristics of butanol-diesel blends

Spray characteristics are among the most important factors that affect compression ignition (CI) engines’ performance and emission levels. Flow visualisation and optical diagnostics have been widely employed in previous and current research as methods for controlling the combustion processes. This paper investigates the spray visualisation of butanol-diesel blends to determine spray characteristics such as spray penetration (S) and Average Sauter Mean Diameter (ASMD) using Ansys Forte under different ambient pressures and temperatures. The spray results showed that the spray penetration length is decreased as a result of the increased ambient pressure, while it is increased as a result of increased injection pressure of all test fuels. An increase in ambient temperature caused pure diesel penetration to become longer and wider, while butanol-diesel blends penetration becomes shorter. The ASMD of the butanol-diesel blend is higher than that of pure diesel at all operating conditions

The impact of injector hole diameter on spray behaviour for butanol-diesel blends

Optimising the combustion process in compression ignition (CI) engines is of interest in current research as a potential means to reduce fuel consumption and emission levels. Combustion optimisation can be achieved as a result of understanding the relationship between spraying technique and combustion characteristics. Understanding macroscopic characteristics of spray is an important step in predicting combustion behaviour. This study investigates the impact of injector hole diameter on macroscopic spray characteristics (spray penetration, spray cone angle, and spray volume) of butanol-diesel blends. In the current study, a Bosch (0.18 mm diameter) and a Delphi (0.198 mm) injector were used. Spray tests were carried out in a constant volume vessel (CVV) under different injection conditions. The test blends were injected using a solenoid injector with a common rail injection system and images captured using a high-speed camera. The experimental results showed that the spray penetration (S) was increased with larger hole diameter. Spray penetration of a 20% butanol-80% diesel blend was slightly further than that of neat diesel. Spray penetration of all test fuels was increased as a result of increased injection pressure (IP), while spray cone angle (θ) was slightly widened due to the increase in either hole diameter or injection pressure. Spray volume of all test fuels was increased as a result of increased hole diameter or injection pressure. Thus, an efficient diesel engine performance can be achieved as a result of controlling injection characteristics, especially when using a promising additive like butanol blended with diesel

The effect of butanol-acetone mixture-cottonseed biodiesel blend on spray characteristics, engine performance and emissions in diesel engine

Increasing energy demands and more stringent legislation relating to pollutants such as nitrogen oxide (NOx) and particulate matter (PM) from mineral fuels used in diesel engines have encouraged the use of biodiesel. Biodiesel fuels produced from non-edible oils have properties comparable to diesel fuel, which make them promising alternative fuels. However, there are some drawbacks associated with biodiesel as fuel for compression-ignition (CI) engines such as high viscosity and higher NOx emissions. Using an alcohol butanol-acetone (BA) or acetone-butanol-ethanol (ABE) mixture is one solution to improve blend efficiency and also to lower NOx emissions. The aim of this paper is to investigate the impact of a BA or ABE mixture blended with cottonseed biodiesel on spray characteristics, engine performance (in-cylinder pressure, brake power (BP) and specific fuel consumption (SFC)) and emission levels (NOx and carbon monoxide (CO)). The results demonstrated that BA and ABE decreased biodiesel viscosity and resulted in improved spray characteristics. BP was reduced while SFC was increased. The peak in-cylinder pressure was comparable at a lower engine speed while being slightly lower at 2000 rpm. The maximum reduction in NOx and CO was shown to be from 10BA90Bd by 13.84% and 41.5% respectively at 2000 rpm

Safe Reinforcement Learning via Observation Shielding

Reinforcement Learning (RL) algorithms have shown success in scaling up to large problems. However, deploying those algorithms in real-world applications remains challenging due to their vulnerability to adversarial perturbations. Existing RL robustness methods against adversarial attacks are weak to large perturbations - a scenario that cannot be ruled out for RL adversarial threats, as is the case for deep neural networks in classification tasks. This paper proposes a method called observation-shielding RL (OSRL) to increase the robustness of RL against large perturbations using predictive models and threat detection. Instead of changing the RL algorithms with robustness regularization or retrain them with adversarial perturbations, we depart considerably from previous approaches and develop an add-on safety feature for existing RL algorithms during runtime. OSRL builds on the idea of model predictive shielding, where an observation predictive model is used to override the perturbed observations as needed to ensure safety. Extensive experiments on various MuJoCo environments (Ant, Hooper) and the classical pendulum environment demonstrate that our proposed OSRL is safer and more efficient than state-of-the-art robustness methods under large perturbations

Experimental study of spray characteristics, engine performance and emission levels of acetone-butanol-ethanol mixture-diesel blends in a diesel engine

This paper investigates spray and engine performance of an acetone-butanol-ethanol (ABE) mixture blended with diesel fuel in a single-cylinder direct injection (DI) diesel engine. Spray images were evaluated using a high-speed camera under 300 bar injection pressure. Engine performance such as brake power (BP), brake-specific fuel consumption (BSFC) and in-cylinder pressure were measured. Exhaust gas emissions such as oxides of nitrogen (NOx), carbon monoxide (CO) and unburned hydrocarbon (UHC) were also assessed. The test was carried out at three engine speeds (1400, 2000 and 2600 rpm) at full load. The experiment results showed that: liquid penetration of ABE-diesel is longer than that of diesel. BP of ABE-diesel blends was comparable with pure diesel at 2600 rpm, while the peak in-cylinder pressure was higher compared to diesel at 2000 rpm. UHC and CO emissions were significantly reduced as a result of the addition of ABE to the neat diesel, while NOx emissions were slightly increased

Effect of air-fuel ratio on temperature distribution and pollutants for biogas MILD combustion

This paper examines the effect of air-fuel ratio for Moderate or Intense Low oxygen Dilution (MILD) combustion using a bluff-body burner. Exhaust gas recirculation was used to dilute the oxidizer stream prior to the combustion chamber. A low-calorie biogas fuel which consists of 60% methane and 40% carbon dioxide were used in the simulations using a Reynolds-averaged Navier–Stokes model with the realizable k-epsilon turbulence model. The chamber temperature distribution was found to be in small ranges and almost homogeneously distributed, verifying that MILD conditions were attained. The performance was evaluated based on the level of pollutants (Unburned hydrocarbons (UHC) and carbon-mono oxide (CO)) produced and measured in the exhaust gas. Slightly lean conditions produced negligible pollutants with some excess oxygen measured in the exhaust gas. Under rich conditions, UHC and CO were produced, but when synthetic air containing oxygen with a mole fraction of 7% was used as the oxidizer instead of ordinary air, these levels were significantly reduced

The simulation of biogas combustion in a MILD burner

This paper discusses the design and development of moderate and intense low oxygen dilution (MILD) combustion burners, including details of the computational fluid dynamics process, step-by-step from designing the model until post-processing. A 40 mm diameter bluff-body burner was used as the flame stabilizer. The fuel nozzle was placed in the center with a diameter of 1 mm and an annular air nozzle with an opening size of 1,570 mm2, and four EGR pipes were used. Non-premixed combustion with a turbulent realizable k-epsilon was used in the simulation. The fuel used is low calorific value gas (biogas).The synthetic biogas was a mixture of 60% methane and 40% carbon dioxide. The simulation was successfully achieved during the MILD regime where the ratio of maximum-to-average temperature was less than the required 23%

Provocations of European Ethnology

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66376/1/aa.1997.99.4.713.pd

Modeling viral and drug kinetics: Hepatitis C virus treatment with pegylated interferon alfa-2b

Administration of peginterferon alfa-2b plus ribavirin results in an early hepatitis C virus (HCV) RNA decay followed by an increase as the drug concentration declines between doses. Upon administration of the next dose 1 week later, the same pattern is observed. We have incorporated pharmacokinetic/pharmacodynamic analysis into a model of viral dynamics to describe the effect that changes in drug concentration and effectiveness can have on viral levels. To illustrate the relationship between pharmacokinetics and viral dynamics, we fit the model to data from four HCV/human immunodeficiency virus co-infected patients, and obtained good agreement with the measured serum HCV RNA levels. We were able to account for the observed increases in HCV RNA, and estimate virion and drug half-lives that are in agreement with previous reports. Models incorporating pharmacokinetics are needed to correctly interpret viral load changes and estimate drug effectiveness in treatment protocols using peginterferon alfa-2b