From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Analysis of engine power output and fuel consumption, comparing supercharged and unsupercharged performance at different compression ratios.
| Identifier | ExFiles\Box 140\1\ scan0212 | |
| Date | 28th March 1938 guessed | |
| -8- The calculated blower power requirement data are shown in Figure 13. The differences in blower power requirement for the two compression ratios resulted from differences in actual air consumption, the data for which are shown in Figure 14. No exact explanation can be offered for the difference in air consumption shown for the two compression ratios, although it seems most likely that they resulted from changes in atmospheric conditions, since the data for the two compression ratios were not all taken on the same day. Slight daily variation in air consumption for a given engine condition were observed during the tests. Data obtained on the same day for the two compression ratios at approximately the same degree of supercharging showed practically the same air consumption in each case. Figure 28 shows this was the case at an engine speed of 1000 r.p.m. for a range of intake manifold pressures between 0 and 30 inches of mercury above atmospheric. Figures 15 shows the power required to motor the engine at the speed and intake manifold pressure considered with no supercharging and with an intake manifold pressure of ten inches of mercury above atmospheric. It is interesting to note that the power required was less when the engine was supercharged than when it was unsupercharged, due to the work of the supercharged air on the pistons during the intake stroke. Power Output And Specific Fuel Consumption Of The Supercharged Engine With Allowances For The Power Charged To The Blower. The net brake horsepower and specific fuel consumption for the engine at maximum power air-fuel ratio and spark advance for each of the tests are shown by Figure 16. The 5.55 to 1 compression ratio engine supercharged showed an increased of 80 percent in power over the unsupercharged engine. The 4.25 to 1 compression ratio engine supercharged showed an increase of 50 percent in power output over the standard engine unsupercharged. The fuel consumption curves probably show a fairly accurate picture of what may be expected in the way of economy as a result of supercharging. The specific fuel consumption of the engine with 5.55 to 1 compression ratio supercharged was practically the same as for the engine unsupercharged in the lower speed ranges, but at the high speeds the engine supercharged was decidedly the better. As might be expected the specific fuel consumption of the engine with lower compression ratio supercharged was higher than either of the other two. | ||