Energy losses are of great significance to the automotive and motorsports industries. Many of these losses are incurred during power transmission through the gearbox. There has been considerable research in this area; however, generally gear losses are not calculated at part load condition, nor are so-called dry sump systems considered outside of motor racing. The method developed by Anderson & Loewenthal, which considers efficiency over part-load conditions is used here to calculate geartrain losses with varying speed, load and temperature conditions in a spur gear type gearbox for motorsport application. Both oil bath (wet sump) and oil jet (dry sump) systems of lubrications are considered. The Changenet method is used to calculate the churning losses in the typical oil bath lubrication system. Seventeen different mineral and synthetic oils were evaluated. At 75 kW engine output, 1200 W were lost in the dry sump gearbox whereas 1320 W were lost in the wet-sump gearbox -in first gear at 10,500 r/min engine speed. The oils studied showed a spread of total drive efficiency of 97.8% to 99% in the most extreme temperature case. From the observation of how efficiency and film thickness relate to operating temperatures, it is clear that tight temperature control is critical to obtain the potential benefits available from oil optimisation. The dry sump gearbox is predicted to be more efficient only above 5000 r/min engine speed.
This chapter is where Dr. Kollmann’s original manuscript starts. His introduction of the fundamental aerothermodynamic principles governing the design of centrifugal (radial) compressors is not in a form that one would find in standard textbooks, vintage or modern. Dr. Kollmann essentially lists the pertinent equations in the form of a ‘crib sheet’ that an experienced engineer would consult in his or her daily work. This is not surprising because, in all likelihood, when he was writing this manuscript (or at least this part of it) Dr. Kollmann did not have access to all his papers and books. In fact, the authors have a suspicion (a rather strong one from the cover page, as shown in the title page of the present book) that Dr. Kollmann wrote this section while he was actually in Allied custody or at ‘home supervision’.
The operating point where the compressor speed lines, and the engine’s operating line meet is critical. Thus, improvement of the efficiency at that point is of paramount importance. Through systematic development of the single-stage supercharger by (i) incremental improvements to the compressor impeller, (ii) the arrangement and development of the diffuser vanes, and (iii) the shape of the outer volute/spiral, significant gains in the performance of the single-stage compressor have been made.
High rotational speeds of the impeller call for careful bearing design and layout, not just those on the supercharger impeller shaft itself but also on any preceding shafts, which may run at lower speed. The question of whether to use plain (journal) bearings or rolling element bearings can only be decided after a complete evaluation of the overall design of the supercharger drive system in question. Journal bearings are in general smaller in outside diameter and despite the higher overall length have a lower weight than rolling element bearings. Journal bearings demand several times the lubricating oil flow rate than rolling element bearings, and they also exhibit high sensitivity to particulates in the oil and the overall quality thereof.
This chapter contains the references listed by Dr. Kollmann himself. Some of the cited books can be found on the used book market, e.g., https://www.abebooks.com/books/used-books.shtml (in original German only). They can also be located in big libraries, e.g., the British Library in London.
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