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Abstract
The report covers a period of six years of research leading to the design and manufacture of a compression ignition rotary engine of 350 hp for use in military vehicles. The work carried out to obtain good combustion and effective gas sealing is described in some detail. Outline drawings and data of the new engine are given and size comparisons are made with present-day engines.
... It is well known (e.g., 18,19) that gas leakage across the apex seals detrimentally affects Wankel engine performance. A side study (not included here for brevity) attempted to simulate this leakage path, using a minimum apex gap of 0.5 mm due to the computational expense of the required fine mesh. ...
... As explained in Section 1.1, compared to reciprocating engines, the Wankel engine suffers from higher heat losses through the wall due to its high surface area-tovolume ratio, particularly around TDC (e.g., 18,19). Wall heat transfer is thus a key factor affecting both work output and thermal efficiency. ...
The Wankel rotary engine offers unrivalled power density as a consequence of having a combustion event every revolution, as well as lightness, compactness and vibrationless operation due to its perfect balance. These attributes have led to its success as a powerplant for unmanned aerial vehicles, and which should also make it an attractive proposition for range-extended electric vehicles. However, it is not currently in production for automotive applications having historically struggled with poor combustion efficiency, and high fuel consumption and hydrocarbon emissions. The purpose of this work is to study the in-chamber flow motion in order to better understand how such limitations may be overcome in future. A 225cc 30 kW Wankel rotary engine is modelled using Large-Eddy Simulation (LES) to ensure turbulent flow features are faithfully recreated, since Reynolds-averaged Navier-Stokes-based approaches are insufficient in this regard. The LES-predicted peak chamber pressure lies within 3.7% of the engine test data, demonstrating good model validation. Combustion simulation parameters are calibrated to match the measured heat release profile, for high-load engine operation at 4000 rpm. Simulation results provide insight into the generation of turbulent structures as the incoming flow interacts with the throttle, intake port, rotor and housing surfaces; how the turbulence breaks down as the combustion chamber is compressed; and how the flame propagates following ignition, leaving a pocket of reactants unburned. Indeed, the computational approach described here allows detailed understanding of the impact of design parameters on the detailed in-chamber flow phenomena, and consequently engine performance and emissions. This will enable the optimization of Wankel rotary engine geometry, port and ignition timing for maximum combustion efficiency and low emissions, reasserting its potential as an effective and efficient prime mover for hybrid and range extended electric vehicles.
During the decades past, the engine industries have witnessed a remarkable upsurge in the research and development (R&D) of modern technologies due to factors such as energy security and environmental concerns. Focus is on improved engine performance, sustainable energy, fuel economy and minimal harmful exhaust emissions. Even though globally large database now captures modern engine technologies, a skillful presentation of those data is a demanding task. Based on this analogy, the authors made a conscious effort to brief audience on the various fuels used in Wankel Rotary Engine (RE) which is a type of internal combustion engine (ICE). Wankel RE various operating models, their merits and demerits regarding modern engine technologies, the type of fuels and their utilization methods and the future prospect of bio-fuel as its engine fuel has been made accessible in a subtle manner in this paper. In summary, this paper provides a wide scope review of basic principles that govern practical Wankel RE design and operation, the widely used single fuels and multi fuels in Wankel RE operation with their properties as well as emissions, and the practical Wankel RE design and operation in the present era and the prospects in the near future. It also outlines simplified frameworks of modern Wankel RE technologies structured in a systematic way to contribute to enhanced engine performance, sustainable energy, reduce fuel consumption and reduce exhaust emissions in this pragmatic field.
The second paper assesses the overall performance characteristics of the differential compound engine (d.c.e.) first reported in (21), designed to constitute an integrated engine-transmission system providing high unit output, combined with outstanding torque characteristics for traction applications.
Experimental results, for both equilibrium conditions and transient response are presented for the original two-stroke c.i. version of the laboratory unit, incorporating the Rootes TS 3 opposed piston engine. Theoretical predictions both for this version, and the later four-stroke version, using the Perkins 6·354 engine, based on the generalized computer approach of the first paper, are also presented.
The unit is then critically compared with existing or prospective traction prime movers using the following criteria.
(1) Fuel economy.
(2) Torque characteristics.
(3) Noise and emission.
(4) Unit specific weight and bulk.
Finally, a projected automotive unit of approximately 2 hp shaft output is described with illustrations to show the potential of the d.c.e. as an alternative engine-transmission system for heavy trucks and off-highway vehicles.
Internal combustion engines can be divided into two groups defined by the behaviour of motion of the centre of gravity of the power output member. The first group contains engines where this motion is either oscillatory along a circular arc or preferably along a straight line (piston in reciprocating engine). The second comprises those engines where the motion is unilateral along a closed path, preferably circular (rotor in rotary engine). In both cases the motion may be at uniform or non-uniform velocity and the power member may additionally rotate at constant or variable velocity about an axis passing through its certre of gravity.
Power plants on the basis of heat engines except for reciprocating internal combustion engines and jet propulsion engines are classified by the authors of the paper as non- conventional ones. The article also presents the results of research carried out in this field by scientists of the Institute of Aeronautics of Riga Technical University. The article describes the two patents. The first patent to be considered was received for a rotary-piston engine, the second one – for the Stirling engine.
The second paper assesses the overall performance characteristics of the differential compound engine (d.c.e.) first reported in (21), designed to constitute an integrated engine-transmission system providing high unit output, combined with outstanding torque characteristics for traction applications.
Experimental results, for both equilibrium conditions and transient response are presented for the original two-stroke c.i. version of the laboratory unit, incorporating the Rootes TS 3 opposed piston engine. Theoretical predictions both for this version, and the later four-stroke version, using the Perkins 6·354 engine, based on the generalized computer approach of the first paper, are also presented.
The unit is then critically compared with existing or prospective traction prime movers using the following criteria.
(1) Fuel economy.
(2) Torque characteristics.
(3) Noise and emission.
(4) Unit specific weight and bulk.
Finally, a projected automotive unit of approximately 2 hp shaft output is described with illustrations to show the potential of the d.c.e. as an alternative engine-transmission system for heavy trucks and off-highway vehicles.