In reply to Duncan's comments, it is indeed possible to change the
size of the entry jet into a pelton wheel type flow meter. The RS
meter is actually supplied with an insert which changes the effective
flow range of the meter. As the size of the jet is increased, the
flow velocity is reduced, This in turn inceases the flow rate at
which the meter will start to read.
It may be possible to increase the bore to a size where the meter does
not read at idle, but reads accurately at modest (low cruise, or
powered descent) rpm upwards. This would still allow measurement of
fuel used over the majority of the flight regime. Any inaccuracies
from startup and taxi/hold would be minimal, and likely to be of the
same order as the uncertainties of tank volume (we all know that
changes) and the absolute calibration of the meter.
I may be able to provide more definitive answers when the
manufacturers reply to my request for info, but I'll keep you posted
on that score.
On the subject of fuel meters for cars, it appears that the majority
of cars don't use a fuel flow sensor. Fuel flow is calculated from
engine speed and injector duty. Does any one have a non-injected car
with a fuel computer? If so that could be a good place to start.
Cheers
Carl #159
|