Design study: A 186 kW lightweight diesel aircraft engine

The design of an aircraft engine capable of developing 186 kW shaft power at a 7620 m altitude is described. The 186 kW design takes into account expected new developments in aircraft designs resulting in a reassessment of the power requirements at the cruise mode operation. Based on the results of this analysis a three phase technology development program is projected resulting in production dates of 1985, 1992, and 2000

Particle growth of nano-silica below the isoelectric point

Nano-silica is one of the most used nano-materials, and its use is rising 5.6% per year to reach a projected 2.8 million metric tons in 2016 with a value of $6.4 billion. The current production methods involve steps with high temperatures resulting in environmentally unfriendly and expensive process. The production of nano-silica by the dissolution of olivine is an interesting alternative to the existing commercial methods because of the good quality of the resulting silica and low energy requirements and CO2 emissions. Olivine nano-silica is produced in a very acidic environment, much more acidic than its isoelectric point. The particle growth of silica under these acidic conditions has only been studied by a few researchers. The main aim of this study is to clarify the mechanism and kinetics of the silica particle growth under these conditions. The silica particle growth was studied with Norwegian olivine in a vigorously stirred reactor at 20 °C with sulfuric acid. The concentration of hydrogen ions was determined at regular time intervals, from which the amount of silica produced was calculated. The silica particle size was measured with the Malvern ZS after passing the samples through a filter of 1 ¿m. The cluster size of olivine silica grows up to 420 nm after 4300 minutes of reaction at 20 ¿C in 2M H2SO4 solution. The mechanism of the growth of silica is likely due to the nucleation of primary particles and subsequent aggregation of these primary particles. Olivine nano-silica does not gel. This behaviour can be due to three reasons: 1) silica polymerizes fast at 90 ¿C in 3M H2SO4 solution, forming particles above 100 nm in a short time; 2) the concentration of small silica colloids is low; and 3) the vigorous mixing in the reactor to keep the olivine particles suspended

Particle growth of nano-silica below the isoelectric point

Nano-silica is one of the most used nano-materials, and its use is rising 5.6% per year to reach a projected 2.8 million metric tons in 2016 with a value of $6.4 billion. The current production methods involve steps with high temperatures resulting in environmentally unfriendly and expensive process. The production of nano-silica by the dissolution of olivine is an interesting alternative to the existing commercial methods because of the good quality of the resulting silica and low energy requirements and CO2 emissions. Olivine nano-silica is produced in a very acidic environment, much more acidic than its isoelectric point. The particle growth of silica under these acidic conditions has only been studied by a few researchers. The main aim of this study is to clarify the mechanism and kinetics of the silica particle growth under these conditions. The silica particle growth was studied with Norwegian olivine in a vigorously stirred reactor at 20 °C with sulfuric acid. The concentration of hydrogen ions was determined at regular time intervals, from which the amount of silica produced was calculated. The silica particle size was measured with the Malvern ZS after passing the samples through a filter of 1 ¿m. The cluster size of olivine silica grows up to 420 nm after 4300 minutes of reaction at 20 ¿C in 2M H2SO4 solution. The mechanism of the growth of silica is likely due to the nucleation of primary particles and subsequent aggregation of these primary particles. Olivine nano-silica does not gel. This behaviour can be due to three reasons: 1) silica polymerizes fast at 90 ¿C in 3M H2SO4 solution, forming particles above 100 nm in a short time; 2) the concentration of small silica colloids is low; and 3) the vigorous mixing in the reactor to keep the olivine particles suspended

Development of the particle and pore structure of silica below the isoelectric point

Nano-silica is one of the most used nano-materials, and its use is rising 5.6% per year to reach a projected 2.8 million metric tons in 2016 with a value of $6.4 billion. The current production methods involve steps with high temperatures resulting in environmentally unfriendly and expensive process. The production of nano-silica by the dissolution of olivine is an interesting alternative to the existing commercial methods because of the good quality of the resulting silica and low energy requirements and CO2 emissions. Olivine nano-silica is produced in a very acidic environment, much more acidic than the isoelectric point of the silica. The particle and pore structure development of silica under these acidic conditions has only been studied by a few researchers. The main aim of this study is to develop a model about the particle and pore formation of silica in very acidic environments. Nano-silicas prepared via the olivine route were analyzed to determine their pore structure and SSANMR. The pore structure was determined using the nitrogen physisorption, NMR and PALS (positron annihilation spectroscopy) techniques. The development of the nano-silica structure during the olivine process can be described by the following steps: 1) initially, soluble silica nucleates and primary particles of around 2 nm are formed; 2) the silica particles grow via a condensation route, forming linear chains; 3) as the growth continues, the silica particles keep increasing in size, resulting in 3D networks; and 4) with time, the aggregates become bigger and more compact. The final result of the olivine process is agglomerates as big as 20 ¿m. In addition, internal pores (also called closed pores) are developed with the reaction conversion degree as the result of condensation of two blocks of silica particles