Internal-combustion engines – Rotary – With compression – combustion – and expansion in a single...
Reexamination Certificate
2000-08-02
2002-05-14
Denion, Thomas (Department: 3748)
Internal-combustion engines
Rotary
With compression, combustion, and expansion in a single...
C123S688000, C123S568120, C418S100000, C418S159000, C055S423000, C138S045000, C138S046000, C060S284000, C060S297000
Reexamination Certificate
active
06386172
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to rotary vane pumping machines, and more particularly, to a variable bandwidth striated charge for use in reducing vacuum pumping losses in a rotary vane internal combustion engine.
2. Description of Related Art
In the operation of conventional internal combustion engines in many applications (e.g. automotive), less than full power is required. It is during these partial-power situations that a great deal of an engine's fuel efficiency can be lost. A typical automotive engine may have an efficiency of 30% at full load, but in real world driving at partial load, this efficiency often decreases to 10% or lower. It is widely accepted that reducing the partial-output efficiency losses is at least as important in improving overall fuel economy in automobiles as achieving minor improvements in peak engine efficiency at full load.
Otto cycle (spark ignition or SI) and diesel (compression ignition or CI) engines have been used extensively in automotive applications. These engines are positive displacement machines. This means that they move air at different rates in roughly linear proportion to the engine speed. The amount of air available for combustion determines the maximum amount of fuel that can be effectively burned and thus the power output. Therefore, one important way of limiting power is to reduce engine speed. Another way of limiting power at a given fuel-air ratio is to restrict the mass flow of air into the engine with a vacuum throttle. Yet another way of limiting power is to reduce fuel flow at a given engine speed and mass flow of air.
Whereas power reduction can result from any of these three methods, significant load reduction can only result from either throttling or leaning of the overall fuel-air ratio for conventional engines. In automotive applications engine speed at a given road speed is typically modified by changing the gearing in discrete steps. Engine speed is rarely continuously variable, and therefore power reduction must often be produced by load reduction alone (i.e., at least one of either throttling or leaning of the overall fuel-air ratio) in many applications such as automotive. Therefore, there exists a need to significantly improve the efficiency at partial load in internal combustion engines in these applications.
The partial-load component of efficiency losses may be broken into two primary contributors, vacuum pumping losses and mechanical friction losses. Both factors contribute significantly to the partial-load component of efficiency losses in SI engines, whereas mechanical friction losses tend to dominate the partial-load component of losses in diesel engines.
FIG. 1
is a graph of efficiency versus load for a standard SI piston engine. Line A shows the engine's efficiency based on losses caused by fuel conversion but without considering vacuum pumping or mechanical friction losses. Line B shows the engine's efficiency based on losses caused by fuel conversion and vacuum pumping losses. Line shows the engine's actual efficiency based on losses caused by fuel conversion, vacuum pumping losses, and frictional losses. As
FIG. 1
shows, at lower load levels, the losses in engine efficiency caused by vacuum pumping and mechanical friction losses are significant.
SI engines are typically governed by a throttle, which controls air flow. A roughly stochiometric mixture is usually required to ensure ignition and flame propagation, when initiated by a spark. Diesel engines do not have this narrow mixture requirement, and can control power output by regulating fuel flow without a throttle. The temperature of the air under high compression of a CI engine allows the robust combustion of very lean mixtures.
Although
FIG. 1
describes the efficiency versus load for a standard SI piston engine, curves A and C for a standard CI engine would be roughly similar in proportion. Diesel engines have long been recognized for their improved fuel efficiency. The lack of a throttle and associated vacuum pumping losses contributes significantly to the efficiency advantage in many applications such as automotive. However, while diesel engines do not suffer from the same vacuum pumping losses as SI engines, the comparatively high compression of the diesel engine coupled with the lack of throttle increases relative friction losses from many of the rotating bearings, such as the crank, rod, and wristpin bearings.
Furthermore, the friction losses necessarily represent a greater contribution for the diesel engine than for the SI engine if both engines are constrained to the same partial load percentage. This fact can be established on a mathematical basis. By eliminating the bulk of vacuum-pumping losses, the diesel engine gains in efficiency—and thus also in output. Therefore additional load reduction is required to achieve the same output. At a given speed, this additional load reduction will further increase the percentage of mechanical friction losses as the operating point moves toward the origin, in a manner similar to that shown in the curves of FIG.
1
.
Therefore, one can see that by substantially reducing only one of either mechanical friction losses or vacuum pumping losses, the other remaining loss will necessarily increase as a percentage loss when constrained to the same output at a given speed. A need therefore exists for a combustion engine which substantially reduces both mechanical friction and vacuum pumping losses so as to provide a substantial improvement in partial load efficiency.
Rotary vane engines can employ roller bearings as primary frictional interfaces and therefore do not suffer from the significant sliding frictional losses of piston engines. However, this dramatic reduction of friction means a larger percentage of the partial load inefficiency comes from vacuum pumping losses in a throttled engine when constrained to the same load, for the mathematical reasons described above. An engine that could simultaneously significantly reduce or substantially eliminate both mechanical friction and vacuum pumping losses at partial loads would offer significant efficiency advantages for many applications such as automotive. A need therefore exists for a low-friction rotary-vane combustion engine that employs a means to significantly eliminate vacuum pumping losses while maintaining the ability to rapidly adjust the load across a wide range of load outputs.
One variety of rotary engines that could be configured under the present invention to avoid vacuum pumping losses are rotary vane combustion engines (more particularly, rotary vane internal combustion engines). This class of rotary vane pumping machine includes designs having a rotor with slots having a radial component of alignment with respect to the rotor's axis of rotation, vanes that reciprocate within these slots, and a chamber contour within which the vane tips trace their path as they rotate and reciprocate is within their rotor slots.
The reciprocating vanes thus extend and retract synchronously with the relative rotation of the rotor and the shape of the chamber surface in such a way as to create cascading cells of compression and/or expansion, thereby providing the essential components of a pumping machine. For ease of discussion, a rotary vane combustion engine will be discussed in detail.
FIG. 2
is a side cross sectional view of a conventional rotary-vane combustion engine.
FIG. 3
is an unrolled view of the cross-sectional view of FIG.
2
.
As shown in
FIG. 2
, the rotary engine assembly includes a rotor
10
, a chamber ring assembly
20
, and left and right linear translation ring assembly plates
30
.
The rotor
10
includes a rotor shaft
11
, and the rotor
10
rotates about the central axis of the rotor shaft
11
in a counterclockwise direction as shown by arrow “R” in FIG.
2
. The rotor
10
has a rotational axis, at the axis of the rotor shaft
11
, that is fixed relative to a stator cavity
21
contained in the chamber ring assembly
20
.
The rotor
10
Denion Thomas
Mallen Research Ltd.
Trieu Thai-Ba
LandOfFree
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