Thanks, Alexander. Sounds like the Q&A was based on having only looked closely at one of the older engines. Swirl injectors are in a similar state in the US as pintles; there are people who use them but they're not very common. Ben On Wed, Nov 13, 2013 at 1:25 AM, contact@xxxxxxx <contact@xxxxxxx> wrote: > I have seen this Q&A before, and was always wondering what exactly is meant > by "more conical Soviet nozzles" and "worse combustion efficiency in Soviet > chambers"? > > Method to design optimal nozzle contour was developed in Soviet Union 1 or 2 > years earlier than Rao developed similar method in USA. First engine with > such nozzle was RD-219 for R-16, developed in 1958-1961. Since then all > Soviet engines were developed with optimal nozzle contour, including of > course all staged-combustion engines. > > The only engines with "conical" nozzles (actually - with "radius" nozzles) > were RD-107 and RD-210...214, developed in first half of 1950s. > > Concerning combustion efficiency: "traditionally" almost all Soviet engines > had swirl injector elements (either single or two components) which provide > better atomization and mixing compared to jet injector elements > "traditionally" used in US engines. Since earlier 1960s, almost all engines > developed in USSR were staged-combustion engines, with swirl injectors for > liquid component and jet injectors for hot gaseous component. Such > combination provides even better atomization and mixing. > > > Best regards > > Alexander Ponomarenko > http://www.propulsion-analysis.com > > > >> Ben Brockert <wikkit@xxxxxxxxx> hat am 12. November 2013 um 20:35 >> geschrieben: >> >> >> Anyone have further info to back this up, or Russian nozzle design >> logic translated into English? >> >> From a powerpoint on nozzles by D. R. Kirk of FIT: >> >> Q: Why do U.S. nozzles look more like a polynomial contour and Soviet >> nozzles look more conical? >> >> A: (Jim Glass, Rocketdyne) >> >> Interestingly, Soviet nozzle designs have a 'different' look to them >> than typical US designs. US designs are ‘truncated Rao optimum’ >> bells, usually designed by method-of-characteristics methods. Soviet >> nozzles, to US eyes, look more conical than ours. Ours have that nice >> ‘parabolic’ look to them - less conical. One would suppose the >> Russians are fully capable of running M-O-C and CFD codes and thus >> their nozzles, if optimum, should look ‘just like’ ours. Since they >> don't, I've always wondered if they know something we do not. In my >> experience, the US is better at combustion engineering (minimal C-star >> losses) but has fairly substantial losses in the nozzle (aerodynamic >> losses). The Russians tend to reverse this, throwing away huge gobs >> of energy due to incomplete combustion and then using a very efficient >> expansion process to get some of it back. The bottom line is both >> design approaches appear to yield roughly the same Isp efficiency... >> One wonders what would happen if one were to mate a US combustor to a >> Russian nozzle… >>