Professor Ju<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Research Area: Transportation and Nanoparticles<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Hypersonics generates enormous heating of the aircraft since the ignition temp is very high<\/p>\n
o \u00a0\u00a0 Necessitates different cooling for the engine stability<\/p>\n
Questions for Professor Ju<\/p>\n
What is an ideal fuel for the engine?<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 depends on the engine.<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 For ground transportation, you don\u2019t want a fuel that gets ignited too fast. You can\u2019t have fuel that has more than 50% ethanol due to corrosion (lubrication issue).<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Aromatic fuel (benzene) is very lubricating.<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 For aircraft, there is a lot of aromatic fuel due to the fact that aircraft engines go at a higher rotation<\/p>\n
Hybrid Cars?<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 The batter is super expensive<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Electric cars are heavily subsidized at the moment, so actual costs of these batteries are a lot more expensive.<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Hybrid will have a good future before electric cars.<\/p>\n
o \u00a0\u00a0 Gasoline has 50x higher power to weight compared to the latest lithium batteries<\/p>\n
o \u00a0\u00a0 Lithium batteries have an inherent limit.<\/p>\n
o \u00a0\u00a0 But Lithium Flouride batteries have a better future than current ones.<\/p>\n
Diesel Engines vs Gasoline Engines?<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 European : 50% diesel engine<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 U.S. : 90% gasoline engine<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 In terms of efficiency, diesel engines are 30% more efficient than gasoline engines.<\/p>\n
o \u00a0\u00a0 Diesel engines does not have a knocking process\u2014we can ramp up the compression ratio much higher than gasoline<\/p>\n
o \u00a0\u00a0 Because of the high pressure, the engines are heavier though.<\/p>\n
o \u00a0\u00a0 Also, diesel engines have more emissions (NOx); thus, Japanese carmakers have steered away from the diesel engines.<\/p>\n
o \u00a0\u00a0 In Europe, diesel engines are very popular.<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 With electric cars coming in, diesel engines might face tougher competition.<\/p>\n
EGR?<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 the temperature of the exhaust coming from the exhaust pipes are very low<\/p>\n
o \u00a0\u00a0 Thus, it is very difficult to use this energy<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Another idea is to use the heat radiating from the engine into electrical energy.<\/p>\n
HCCI<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 trying to combine the merits of diesel engines and the gasoline engines<\/p>\n
o \u00a0\u00a0 higher compression with lower emissions<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Premix vs Diffusion<\/p>\n
o \u00a0\u00a0 Candle flame is a diffusion; they mix as they burn<\/p>\n
o \u00a0\u00a0 Premix -> oxygen and fuel are \u201cpremixed\u201d before you burn<\/p>\n
o \u00a0\u00a0 Diesel is diffusion and gasoline is premixed<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Instead of using a spark plug, you ignite it by compression with a very low premixed fuel<\/p>\n
o \u00a0\u00a0 Temperature is very low<\/p>\n
o \u00a0\u00a0 But controlling the ignition is hard<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 HCCI concept has been around for 30 years but perfecting is hard<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Diesel cannot be fully premixed<\/p>\n
o \u00a0\u00a0 If it is premixed then as soon as compression happens, it will ignite.<\/p>\n
Gas Turbines<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 ground turbine has duel design\u2014one from the gas turbine and the other from steam turbine<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Most efficient gas turbine<\/p>\n
o \u00a0\u00a0 Supercritical steam turbine: the efficiency can be up to 40%<\/p>\n
o \u00a0\u00a0 Gas combined with this supercritical steam turbine: 62%<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Professor Ju thinks natural gas will stay due to the fact that the efficiency is so high.<\/p>\n
Lead<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Octane number: indicator of how good the fuel is in anti-knocking<\/p>\n
o \u00a0\u00a0 Lead is very cheap that increases the octane number<\/p>\n
o \u00a0\u00a0 Now they use aromatics: Toulene<\/p>\n
Valve Overlap<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 when the intake valve and exhaust valve is open at the same time.<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 What determines how much overlap you have? Why do you even have it at all?<\/p>\n
o \u00a0\u00a0 Because when the exhaust valve is open, the exhaust gas coming out still has inertia and creates a vacuum of sorts, which helps to intake the gas.<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 In a high performance engine, you would see more overlap.<\/p>\n
Geometry of the pistons<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 depends on the cam shaft<\/p>\n
What\u2019s the future?<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 With gas so cheap, he doesn\u2019t think that the gasoline and diesel engine will go away<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Hybrid engines will continue to increase.<\/p>\n
– \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Hydrogen has very low energy density<\/p>\n
o \u00a0\u00a0 To do the compression, you waste a lot of energy.<\/p>\n","protected":false},"excerpt":{"rendered":"
Professor Ju Q&A Session Professor Ju – \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Research Area: Transportation and Nanoparticles – \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Hypersonics generates enormous heating of the aircraft since the ignition temp is very high o \u00a0\u00a0 Necessitates different cooling for the engine stability Questions for Professor Ju What is an ideal fuel for the engine? – \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 depends on the … Continue reading “Tuesday, March 24th, 2015”<\/span><\/a><\/p>\n","protected":false},"author":6,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"class_list":["post-74","post","type-post","status-publish","format-standard","hentry","category-diary"],"_links":{"self":[{"href":"https:\/\/commons.princeton.edu\/57-tiger-cub\/wp-json\/wp\/v2\/posts\/74","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/commons.princeton.edu\/57-tiger-cub\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/commons.princeton.edu\/57-tiger-cub\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/commons.princeton.edu\/57-tiger-cub\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/commons.princeton.edu\/57-tiger-cub\/wp-json\/wp\/v2\/comments?post=74"}],"version-history":[{"count":1,"href":"https:\/\/commons.princeton.edu\/57-tiger-cub\/wp-json\/wp\/v2\/posts\/74\/revisions"}],"predecessor-version":[{"id":75,"href":"https:\/\/commons.princeton.edu\/57-tiger-cub\/wp-json\/wp\/v2\/posts\/74\/revisions\/75"}],"wp:attachment":[{"href":"https:\/\/commons.princeton.edu\/57-tiger-cub\/wp-json\/wp\/v2\/media?parent=74"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/commons.princeton.edu\/57-tiger-cub\/wp-json\/wp\/v2\/categories?post=74"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/commons.princeton.edu\/57-tiger-cub\/wp-json\/wp\/v2\/tags?post=74"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}