Basic Theory And Reasearch Of A Twin-rotor Piston Engine

Reciprocating piston engine and rotary piston engine are the two main traditionalpiston engines. After a hundred years’ effort to now, reciprocating piston engine iswidely used in cars, airplanes, ships and other forms of transportation because of itsefficiency and wide power range. Recently, one-man flight vehicle, and unmaned airvehicles, and other new high-compact transportations have a promising future, but thereare no engines available with the desirable attributes. Conventional piston engines havebeen developed to a near-perfect state with further improvement becoming ever moredifficult and costly to achieve. These engines always suffer from systematic losses suchas complex and costly valve systems, a high level of vibration and small power densitycaused by their mechanisms. In addition, by realizing the crisis of global fuels shortageand the need of a future engine with higher power density higher efficiency, peoplehave been devoted to exploring or reconsidering other engine designs.This work is supported by national pre-research foundation. Based on an olddifferential engine concept, it aims to invent an engine named by Twin-Rotor PistonEngine (TRPE). With advantages of multiple power storkes per revolution of the outputshaft, high volumetric output and variable compression ratio, This engine has thepotentiality to solve the above crisis in theory. Some basic theory and powertransmission device of TRPE are studied in this paper, which provides an importanttheoretical basis and technical guidance for the further production of the experimentalprototype. To sum up, the main results in this paper contain the following areas:(1) The structure and work principle of TRPE with N vane pistons are studied.Analysis and comparison with traditional engine in some aspects such as combustiongas force transmission, volume change of working chamber, power frequency, piston’svelocity, and power density are introduced.The overall design of TRPE is proposed.Layout of eliminating the inertia force and sealing the working chamber of TRPE isdesigned. Power transmission device of TRPE is composed of a Power Cylinde Module(PCM) and a Differential Velocity Mechanism (DVM). TRPE is expected to have threekey technical advantages for attaining higher power density than any available pistonengine: the first is sixteen or more power strokes per revolution of the output shaft andmore than two symmetrical working chambers exporting power at any time; the secondis symmetrical structure and well balanced kinetics; the third is performing thefour-stroke cycle without using the valve mechanism.(2) Basic design theory of realizing high power density of TRPE is built. A newtheory of “mechanism” adapt to “combustion” is introduced and used for guiding thedesign procedure of TRPE: The first step is getting a change law of working chamber volume which fit the new energy and cycle. The second step is getting the motion of thetwo rotors based on the first step. The third step is choosing the suitable mechanismwhich can restrict the two rotors’ motion follow the special pattern after mechanismsynthesize, kinetic design, experiment test, etc.(3) Design and Analysis of Mathematical model of PCM are done. Basicrelationship of components of PCM is derived. The conditions of intake, compression,combustion, and exhaust are presented. The displacement and the instantaneous flow ofthe engine are deduced. Numerical examples that illustrate the kinematic characteristicswere presented. Expression of the compression ratio of the two engine mechanismswere derived. The instruction and effective performance of TRPE is calculated. The gastorque in a TRPE is modeled using adiabatic approximation with instantaneouscombustion. Mathematical modeling of gas force transmission is built. Differentvariation patterns of the volume change of working chamber are introduced. It’sconcluded that: the vector sum of combustion gas forces acting on each rotor piston inTRPE is a pure torque, and the combustion gas rotates the rotors while compresses thegas in the compression chamber at the same time.The value of gas torque in TRPE willfall to be less than zero before the time when the combustion phase is finish; It isnecessary to design the moment based on the in order to export the maximum of energy.(4) Some DVMs based on ordinary gear train, cycloid, or cam are invented whichis assembled with corresponding PCM with N vane pistons. DVM is a new combinedmechanism which can be applied in piston engine, pump, compressor, etc. DVM is aone degree-of-freedom mechanism which has one input part and two output parts. Theinput part rotates with the same speed. The relative motion between the two output partsshould follow a special law which in accordance with “combustion”. Synthesization andanalysis method of DVM is built. Method of forming a new DVM is summerized.Kinematic analysis and design of DVM is done. Three3D-models of powertransmission device are designed. DVM is composed of the non-uniform mechanismand the period mechanism, which constrain the two rotors fixed inside the housingrotating with periodical nonuniform velocity. Thus the volume of the working chambersvaries, and opens and closes periodically.(5) Two prototypes of TRPE had been designed and manufactured. One prototypeis based on cycloid. The other is based on cam. These prototype is intended for highpower density engines and can produce more power strokes per shaft revolution. Somekey technique parameters such as the relationship between the number of vane pistons,the gear ratio, and the number of petals on cam are determined. Kinematic analysis andsimulation of three TRPEs based on epicycloid, hypocycloid, and pericycloidal curveare presented. Kinematic synthesis and transmission quality of TRPE based on cycloidare done. A suitable TRPE which rotor may cease can be designed as the gear ratio, the number of vane pistons, and the angle of vane piston are given. Parametric designmethod of TRPE which follow a special law is presented. The pattern of workingchamber volume adapted to “combustion” can be created by the synthesis of DVM, thefuction synthesis of mechanism based on cycloid, and the cam groove which mayachieve any motion of the rotor. Two prototypes of TRPE mechansim and theircorresponding operation experiment are carried out. The interference and collisionproblem among the vane pistons is analysed and solved.