A method of operating a wheeled vehicle, said method comprising the steps of:
- (a) providing an engine mounted in said vehicle and coupled to at least one vehicle wheel for its propulsion and braking, said engine including at least two cylinders and a cylinder chamber within each of said at least two cylinders,
- (b) providing an air-reservoir means mounted in said vehicle and connected to said engine for receiving, storage, and discharge of compressed air,
- (c) providing a gas exchange controlling means for accommodating and controlling gas flow into, inside, and out of said engine and between said engine and said air-reservoir means,
- (d) operating said engine in a compression-braking mode driven by a vehicle momentum in response to a demand for a vehicle braking force, when said vehicle is in motion and a vehicle braking force is needed, by repeatedly performing a compression-braking cycle, during which air is received from outside atmosphere into at least one of said at least two cylinders, compressed there, transferred to another at least one of said at least two cylinders, subjected to at least one additional compression, and displaced into said air-reservoir means for storage therein,
- whereby energy of the vehicle motion is transformed into energy of compressed air stored in said air-reservoir means,
- whereby said at least one additional compression increases said vehicle braking force, and whereby an increase in temperature of said air, associated with said at least one additional compression, reduces the mass of air required to absorb said energy of vehicle motion and reduces the required volume of said air-reservoir means, and
- (e) operating said engine in a prime mover mode propelling said vehicle when vehicle propulsion force is needed, said prime mover mode including:
- (A) operating said engine in a mode selected from a variety of propulsion modes comprising:
- (1) a first propulsion mode including repeated performance of a multi-stage air-motor cycle, during which a charge of compressed air is received from said air-reservoir means, subjected to at least two successive stages of expansion in said at least two cylinders, and exhausted into said outside atmosphere, whereby said vehicle is propelled without any fuel being consumed,
- (2) a second propulsion mode comprising:
- repeated performance of a two-stroke air-motor cycle in at least one of said at least two cylinders, said two-stroke air-motor cycle including a first stage of expansion of a compressed-air charge received from said air-reservoir means into said cylinder chamber and expulsion of said compressed-air charge from said cylinder chamber, and
- repeated performance of a hybrid four-stroke cycle in another at least one of said at least two cylinders, said hybrid four-stroke cycle comprising two power strokes:
- a first power stroke including a second stage of expansion of said compressed-air charge during a first volume-increasing stroke, and a second power stroke including expansion of combustion gas, produced as a result of fuel combustion, in said cylinder chamber during a second volume-increasing stroke, whereby work performed during said first power stroke is added to work performed during said second power stroke,
- (3) a third propulsion mode comprising:
- repeated performance of a two-stroke air-motor cycle in at least one of said at least two cylinders, said two-stroke air-motor cycle including a first stage of expansion of a compressed-air charge received from said air-reservoir means into said cylinder chamber and expulsion of said compressed-air charge from said cylinder chamber, and
- repeated performance of a hybrid two-stroke internal-combustion cycle in another at least one of said at least two cylinders, during which said compressed-air charge is received into said cylinder chamber and used for combustion during the same cycle, whereby energy of said compressed-air charge supplements the energy released in combustion,
- (4) a fourth propulsion mode including operating said engine in a conventional internal-combustion mode receiving air from said outside atmosphere, and
- (B) changing said engine operation from one propulsion mode to another one selected from said variety of propulsion modes.