CNG-diesel dual fuel engine: a review on emissions and alternative fuels

This review paper is focusing on the investigations and studies on emissions of applying the Compressed Natural Gas (CNG) in the CNG-Diesel engines. As well as, the paper is highlighting studies that involved in the search for alternative fuels to be used for less emissions and good performance vehicles. Moreover, illustrating the developments occurred in this field for the previous five years, from year 2010 to year 2015. And, as observed, many researches indicate that there is a significant decreasing in emissions in the existence CNG-Diesel and other alternative fuels when comparing with the conventional pure diesel heavy duty vehicles engines. Furthermore, there are some attempts of finding alternative fuels were discussed in this paper

Design and development of embedded system to control motorized CNG-air mixer for diesel dual-fuel engine

The world grows in population with rising demand for energy. The environment is much affected by emissions from excessive usage of energy sources, particularly the fossil fuels in transportation, which are producing high amount of Carbon Dioxide (CO2). Concerns over pollution and climate change issues are motivating researchers and engineers to find robust solutions. One of the challenges is to discover low CO2 emission fuels. For instance, natural gas emits up to 70% percent less CO2 than diesel fuel. As a result, the invention of dual-fueled engines took place as a reliable alternative. Diesel-CNG dual fuel (DDF) engine is one of the best approaches to protect the environment, reduce energy consumptions and eliminate pollution. Since it uses diesel and compressed natural gas (CNG), the DDF engine shows very low emissions compared to conventional diesel engine. The DDF engine for the commercial vehicles uses manual CNG-air mixer to partially replace the diesel fuel with the CNG. The proposed motorized CNG-air mixer (MCM) was designed and fabricated to replace the manually actuated CNG-air mixer which needs further optimizations. However, the proposed MCM mixer offers the ability to electronically control and optimize CNG-air mixture and eventually enhance its quality. The objective is to design, simulate and develop an embedded system to control the opening and closing of CNG inlet valve inside the proposed MCM mixer. This embedded system aimed to control bi-polar stepper motor in bi-directional technique by using the high-speed and low-cost PIC16F887 microcontroller chip. The stepper motor was derived by the ASTROSYN P403 stepper motor driver. The inputs of the system were from potentiometers/ sensors.The complete integrated system was simulated and tested as a prototype. The embedded system has 100% accuracy of the simulation and experimental results of PWM1 and PMW2 duty cycle. It has good accuracy up to 75% when comparing the simulation and the experimental response of settlement delay time of RPM input signals. As a conclusion, the success in operating and controlling the stepper motor in the proposed MCM mixer indicated that the embedded system was successfully designed, simulated and developed

SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study

Background: Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling. Methods: The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18-49, 50-69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty. Results: NNVs were more favourable in surgical patients than the general population. The most favourable NNVs were in patients aged 70 years or more needing cancer surgery (351; best case 196, worst case 816) or non-cancer surgery (733; best case 407, worst case 1664). Both exceeded the NNV in the general population (1840; best case 1196, worst case 3066). NNVs for surgical patients remained favourable at a range of SARS-CoV-2 incidence rates in sensitivity analysis modelling. Globally, prioritizing preoperative vaccination of patients needing elective surgery ahead of the general population could prevent an additional 58 687 (best case 115 007, worst case 20 177) COVID-19-related deaths in 1 year. Conclusion: As global roll out of SARS-CoV-2 vaccination proceeds, patients needing elective surgery should be prioritized ahead of the general population