contents of this page are
from "ELEMENTS OF FRASCA ROTARY ENGINE DESIGN"*
*Copyright © 1998 by Joseph F. Frasca
STRUCTURE AND OPERATION
Frasca Rotary Engine
has a casing and a rotor in the casing.
rotor is journaled
to rotate in the casing and has a power output shaft.
cavity about the rotor output shaft axis (i.e. rotor axis) is formed by
and between the rotor and casing in the FRE.
the annular cavity are the wave surface on the rotor and the face
on the casing.
hollow ring like space formed between the casing and the rotor around
power shaft axis.
walls are part casing surface and across from the casing surface, part
a plurality of circumferential spaced slots which extend radial to the
is mounted in each slot for pivotal extension into the annular cavity.
pivot points are a constant radial distance from the power output
axis and a circle about said axis which includes the partition pivot
is referred to as the pivot circumference.
[ i.e. the annular space about the rotor axis formed by and between
wave surface and the casing face surface ] may have different
about the pivot circumference in different FRE designs.
orientation is indicated by the face surface angle.
form a plurality of spaced VVC in the annular cavity circumferential
Chamber [ i.e. a working chamber] is formed by and between consecutive
partitions in the annular cavity and the cavity walls.
power generating cycles of the FRE occur in each VVC during its
traverse of the annular cavity with rotor rotation.
has fuel injectors and intake and exhaust channeling.
intake and exhaust channeling always communicating with their
has at least one undulation in volume (i.e. a variation in cross
area from one location to another) caused by an undulation [in] the
wave surface of the cavity and the annular cavity undulation rotates
the rotor about the rotor axis.
extends pivotally into the annular cavity through its slot in the
annular cavity surface; i.e. the face surface.
pivotal motion is effected by rotor cams or a rotor cam-spring (or
loading means) combination located outside of the annular cavity and
high temperature and pressure extremes therein.
edge(s) shape proximal to the rotor wave surface (i.e. the partitions'
gap edge) conforms with the wave surface shape and never abuts the wave
a gap between a partition's edge at the wave surface and the wave
annular cavity rotation, the rotor cam surface varies each partition's
pivotal extension into the annular cavity so [that each partition ](
remains very close to the rotor wave surface in annular cavity
and combustion regions.
vary as the annular cavity undulation traverse their fixed positions.
rotation with the rotor, the rotor's cam mechanisms pivot the partition
into and out of the ring so that they remain close to and maintain a
with the rotor's ring surface (the wave surface).
chambers (VVC) in the ring therefore vary in volume as the ring moves
their casing locations.
have at least one undulation, the combustion undulation, which, with
rotation, traverses each VVC location causing the VVC's cyclic
rotor surface (the wave surface) in a two cycle engine has a variation
in distance from the ring's casing surface (the face surface) called
undulation, rotating with the rotor, moves by a working chamber's
causing its change in volume.
point to the annular cavity, the VVC are seen to rotate while the
each VVC during its traverse from the beginning to end of a 2-cycle
undulation communicates first with the high pressure air intake port,
a VVC arc distance along (an isolation region) in its traverse, [the
is fuel injected.
the VVC's fuel-air mixture is ignited by the flow of combustion
mass through the gap at the partition separating it from its
VVC preceding it in annular cavity traverse.
the combustion involved gases in the VVC, acting on the rotor wave
drive the rotor in rotation while the VVC with said rotation increases
in volume and continues its traverse of the undulation.
of an annular cavity combustion undulation from a VVC's fuel injection
to the end of its volume increase is referred to as the cavity's or
undulation's "combustion region".
on auto ignition ( i.e. FRE not operating on a diesel [type] cycle)
an ignitor to initiate combustion in the annular cavity; thereafter,
VVC's air-fuel mixture is ignited on fuel injection by the flow of
from the VVC preceding it in the combustion region through the ever
gap between their common partition and rotor wave surface.
of the annular cavity, the VVC decreases in volume and while doing so
expels its products of combustion to outside the engine via the cavity
undulation's exhaust port in the rotor wave surface.
port the combustion products are conveyed by the rotor exhaust
to casing exhaust channeling to outside the engine.
annular cavity traverse (combustion undulation traverse), the VVC
at minimum volume in the annular cavity and thereafter traverses the
arc necessary to isolate the rotor's exhaust port from the high
intake port, usually a VVC arc.
of this isolation region, the VVC again communicates with the high
intake port and begins again the power generating cycle.
of an annular cavity combustion undulation in which a traversing VVC
in volume is referred to as the cavity's or combustion undulation's
of the FRE has, in addition to a combustion undulation, a compression
in its annular cavity.
the compression undulation in its traverse of the annular cavity first
increases in volume and while increasing in volume communicates with a
fresh air intake port in the rotor supplied by corresponding casing
at maximum volume, the VVC's communication with the rotor's fresh air
port ends and the VVC's volume begins decreasing while the rotor works
to compress its fresh air contents.
volume in its compression undulation traverse the VVC then enter the
cavity's isolation-injection-ignition region.
of the IIIR, the isolation region, assures that VVC fuel injection
when the VVC is effectively out of the compression undulation.
region in its annular cavity traverse, the VVC is in the annular cavity
combustion undulation where it functions like a VVC in the 2-cycle
abutments between relatively moving surfaces of the FRE's VVC are not
and are replaced by very small clearances which permit free
relative motion between said surface.
eliminate parts wear, inter-part heat transfer and wiping friction
and friction power losses eliminated in Frasca Rotary Engine designs
replaced with a permitted, albeit, smaller power loss resultant the
flow from the VVC via said clearances.
with two different
annular cavity profiles are discussed in this manual.
most developed has an annular cavity profile based on the partition
formula: r = a + N, and the second, the CIR engine design, has a
section for an annular cavity profile.
design relies on a set of twenty-four, forty-one term expansions to
determine a VVC's volume at any location in the annular cavity.
the coefficients for these expansions using an 8088 PC without NPU took
a full day back when I was doing the basic engineering design work for
the engines; therefore, a fuller development of the CIR engine design
using a reasonably modern PC, it takes less then a minute to generate
same expansion coefficients.
has the particular attraction of allowing very large engine
with very small partition displacements < 5 degrees .
displacements in the first engine type would require partition
of 20 degrees and greater
course in such
CIR engines, the partitions' inertial loads to the rotor cam surface
be very large; however, use of partitions with distal guides should
reduce this rotor cam load.
very low pressure
FRE, with its large tolerances, lower operating temperatures and low
pressures should prove an excellent engine systems test bed.