The Deviation Function Method of Rotary Engine Design by Geometric Parameters

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Sarah Warren Rose ◽  
Daniel C. H. Yang
Keyword(s):  
Compression Ratio ◽  
Design Method ◽  
Geometric Parameters ◽  
Performance Criteria ◽  
Engine Operation ◽  
Deviation Function ◽  
Rotary Engine ◽  
Engine Design ◽  
K Factor ◽  
Wankel Engine

Rotary engines require seals inserted into each rotor apex to maintain contact with the housing and prevent leaks during internal combustion. These seals are called apex seals and their effectiveness directly influences the engine operation and efficiency. The deviation function (DF) method of rotary engine design has several advantages over the conventional design method with regard to the apex seals, and also finds many more possibilities. The DF method can be used to incorporate the profile of the apex seal into the design process and the rotor profile itself. In the DF method, the seal profile is used as a generating curve and the housing bore profile is a generated curve. The housing is conjugate to the apex seal, and therefore conforms to the seal profile, unlike the conventional rotary engine. Another advantage the DF method has over the conventional method is that different apex seal profiles can be used, resulting in a larger variety of rotary engine designs. This paper introduces the DF method of rotary engine design and selection by the geometric parameters rotor radius, R, and eccentricity, l. In conventional rotary (Wankel) engine design, these parameters are used as a ratio called the K factor. The K factor uniquely identifies a conventional rotary engine profile and is therefore used to associate performance criteria such as displacement, compression ratio, and apex sealing. The DF method can be used to employ the same ratio as a selection tool. Instead of a single profile for each K factor, there is a range of possible DF-designed engine profiles associated with each R/l ratio. The resulting design flexibility is shown using two example deviation functions and the design criteria swept area and maximum theoretical compression ratio. Furthermore, the R/l ratio is not an indication of apex sealing effectiveness because the DF method of rotary engine design and selection separates the engine profile geometry from the apex seal geometry. An apex sealing index is presented to show how the DF method can be used to quantify, analyze, and improve apex sealing.

Leakage Flow Analysis for a MEMS Rotary Engine

2003 ◽  
Author(s):  
Joshua D. Heppner ◽  
David C. Walther ◽  
Albert P. Pisano
Keyword(s):  
Power System ◽  
Compression Ratio ◽  
Flow Analysis ◽  
Design Parameters ◽  
Working Fluid ◽  
Leakage Flow ◽  
Engine Operation ◽  
Rotary Engine ◽  
Leakage Flows ◽  
Macro Scale

An internal leakage flow analysis is presented for a MEMS fabricated rotary engine in order to establish design parameters for micro engine sealing systems. This research is part of the MEMS Rotary Engine Power System (REPS) group effort to develop a portable power system based on an integrated generator and Wankel rotary internal combustion engine. In order to have acceptable system efficiency, it is necessary to suppress internal leakage and thereby maintain a critical level of compression ratio. There are two inherent leakage paths in rotary engines, which result in blowby and reduced compression ratio: leakage around the apexes of the rotor and leakage across the rotor faces. These sealing issues arise due to the large pressure gradients, which occur along these leakage paths in the combustion chamber. It is the aim of this work to examine the effects of reduced scale on both traditional and novel rotary engine apex sealing mechanisms. In contrast to the macro scale, viscous forces have an increased importance in micro scale engines since Re~.01. A simplified Poiseuille-Couette flow model has been developed to analyze the leakage flows of rotary type engines. Since the Reynolds number for the MEMS REPS is extremely small, the model assumes that the flow is laminar, viscous, incompressible, and steady with air as the working fluid. The model indicates that if a 1 μm gap can be maintained between the housing and moving parts (rotor apexes and faces), leakage flows at expected engine operation speeds will only reduce the compression ratio from 8.3:1 to 6.1:1 so long as the rotation speed is greater than 10,000 rpm. It is doubtful that a traditional or simple micromachine design will yield such a gap and therefore several novel, integrated sealing approaches are under investigation. The model will determine design specification for one of these approaches, an integrated cantilever flexure apex. In conjunction with the theoretical model, a scaled engine experiment at the macro scale is used to verify the modeling effort. The scaling of the experiment complies with Reynolds scaling and ensures that Hele-Shaw flow within the leakage paths is maintained. The experiment does not operate as a functional engine, rather the experiment is designed to maintain a precise clearance between the rotor and housing. In order to preclude additional pressure driven flow effects, an electric motor is used to spin the rotor and simulate the rotation expected due to the combustion pressure acting on the rotor face.

Geometric design and analysis of scroll compressors with a novel circular involute modified wrap

2021 ◽  
pp. 095440892110530
Author(s):  
Jun Wang ◽  
Yi Han ◽  
Zhoujin Xi ◽  
Zengli Wang ◽  
Dong Cui
Keyword(s):  
Compression Ratio ◽  
Geometric Model ◽  
Geometric Parameters ◽  
Circular Arc ◽  
Design Flexibility ◽  
Study Results ◽  
Temperature Load ◽  
Central Regions ◽  
Working Performance ◽  
And Performance

The scroll geometry in the central region of the scroll wrap plays a crucial role in determining the working performance of scroll compressors. In order to improve the comprehensive performance of scroll wraps, in this study, a novel circular involute modified wrap was put forward, in which the central and peripheral wrap profiles were connected by a circular involute in the central regions, so that a pair of fully smooth and correct meshing scroll wraps were generated. A geometric model of the involute modified wrap were proposed, and then equations of the wrap profiles and relations between geometric parameters were derived. Effects of geometric parameters on the shape and performance of the involute modified wrap were discussed in detail. Furthermore, the compression ratio of the involute modified wrap was studied by numerical simulation, and the deformation of the involute modified wrap produced by temperature load and pressure load was calculated, compared with the conventional circular arc modified wrap under the same geometric shape of scroll compressors. Study results demonstrate that the proposed involute modified wrap may simultaneously improve the compression ratio and the strength of wrap head for scroll compressors; in addition, the involute modified wrap is good for design flexibility, and therefore is superior to the circular arc modified wrap.

scholarly journals Lead and lag controller design in fractional-order control systems

2019 ◽  
Vol 52 (7-8) ◽  
pp. 1017-1028
Author(s):  
Tufan Dogruer ◽  
Nusret Tan
Keyword(s):  
Control System ◽  
Control Systems ◽  
Fractional Order ◽  
Fourth Order ◽  
Controller Design ◽  
Design Method ◽  
Performance Criteria ◽  
Order System ◽  
Fractional Order Control ◽  
Minimum Error

This paper presents a controller design method using lead and lag controllers for fractional-order control systems. In the presented method, it is aimed to minimize the error in the control system and to obtain controller parameters parametrically. The error occurring in the system can be minimized by integral performance criteria. The lead and lag controllers have three parameters that need to be calculated. These parameters can be determined by the simulation model created in the Matlab environment. In this study, the fractional-order system in the model was performed using Matsuda’s fourth-order integer approximation. In the optimization model, the error is minimized by using the integral performance criteria, and the controller parameters are obtained for the minimum error values. The results show that the presented method gives good step responses for lead and lag controllers.

Designing Optimal Origami Structures by Computational Evolutionary Embryogeny

2014 ◽  
Author(s):  
Wei Li ◽  
Daniel A. McAdams
Keyword(s):  
Design Method ◽  
Center Of Mass ◽  
Computational Design ◽  
Design Methods ◽  
Performance Criteria ◽  
Pattern Design ◽  
Modern Computer ◽  
Evolutionary Operators ◽  
Origami Engineering ◽  
Profile Position

As the advantages of foldable or deployable structures are being discovered, research into origami engineering has attracted more focus from both artists and engineers. With the aid of modern computer techniques, some computational origami design methods have been developed. Most of these methods focus on the problem of origami crease pattern design — the problem of determining a crease pattern to realize a specified origami final shape, but don’t provide computational solutions to actually developing a shape that meets some design performance criteria. This paper presents a design method that includes the computational design of the finished shape as well as the crease pattern. The origami shape will be designed to satisfy geometric, functional, and foldability requirements. This design method is named computational evolutionary embryogeny for optimal origami design (CEEFOOD), which is an extension of the genetic algorithm (GA) and an original computational evolutionary embryogeny (CEE). Unlike existing origami crease pattern design methods that adopt deductive logic, CEEFOOD implements an abductive approach to progressively evolve an optimal design. This paper presents how CEEFOOD — as a member of the GA family — determines the genetic representation (genotype) of candidate solutions, the formulation of the objective function, and the design of evolutionary operators. This paper gives an origami design problem, which has requirements on the folded-state profile, position of center of mass, and number of creases. Several solutions derived by CEEFOOD are listed and compared to highlight the effectiveness of this abductive design method.

Prediction of Peak Cylinder Pressure Variations Over Varying Inlet Air Condition of Compression-Ignition Engine

2005 ◽  
Author(s):  
Gong Chen
Keyword(s):  
Air Temperature ◽  
Compression Ratio ◽  
Design Parameters ◽  
Compression Ignition ◽  
Cylinder Pressure ◽  
Compression Ignition Engine ◽  
Engine Design ◽  
Peak Cylinder Pressure ◽  
Temperature And Pressure ◽  
Cylinder Compression

Peak cylinder pressure of a compression-ignition engine can be affected by engine inlet air condition such as its temperature and pressure. The variation of peak cylinder pressure due to varying inlet air temperature and pressure is analytically studied in this paper. An analytical model is developed and thus the variations of peak cylinder pressure can be predicted along with inlet air temperature or pressure varying. It is indicated that cylinder compression ratio (CR) and intake air boost ratio (pm0/pi0) play significant roles in affecting the variation of peak cylinder pressure over inlet air temperature and pressure, and the pressure variation is proportional to CRk and pm0/pi0. The predicted results are compared to those from engine experiments, and show a close agreement. The prediction also includes the investigation of the variation in peak cylinder pressure due to varying the cylinder TDC volume. Results from the analytical studies are presented and show that the change in pmax versus a change in the volume is also affected by compression ratio. This indicates that for a certain change in the clearance volume, a higher compression-ratio configuration would produce a greater change in pmax than a lower compression-ratio would with the rest of the engine design parameters remaining unchanged.

scholarly journals Two-Stroke Wankel Type Rotary Engine: A New Approach for Higher Power Density

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4096 ◽  
Author(s):  
Osman Akin Kutlar ◽  
Fatih Malkaz
Keyword(s):  
Power Density ◽  
Combustion Engine ◽  
Power Stroke ◽  
Specific Power ◽  
Stroke Frequency ◽  
Rotary Engine ◽  
Port Area ◽  
Speed Range ◽  
Wankel Engine ◽  
Stroke Cycle

The Wankel engine is a rotary type of four-stroke cycle internal combustion engine. The higher specific power output is one of its strong advantages. In Wankel rotary engine, every eccentric shaft revolution corresponds to one four-stroke cycle, whereas conventional reciprocating engine fulfills four-stroke cycle in two crankshaft revolutions. This means the power stroke frequency is twice that of conventional engines. Theoretically, application of two-stroke cycle on Wankel geometry will duplicate the power stroke frequency. In this research, a single-zone thermodynamic model is developed for studying the performance characteristic of a two-stroke Wankel engine. Two different port timings were adapted from the literature. The results revealed that late opening and early closing port geometry (small opening area) with high supercharging pressure has higher performance at low speed range. However, as the rotor speed increases, the open period of the port area becomes insufficient for the gas exchange, which reduces power performance. Early opening and late closing port geometry (large opening area) with supercharging is more suitable in higher speed range. Port timing and area, charging pressure, and speed are the main factors that characterize output performance. These preliminary results show a potential for increasing power density by applying two-stroke cycle of the Wankel engine.

scholarly journals Seismic design and analysis of reinforced concrete buckling-restrained braced frame buildings with multi-performance criteria

2019 ◽  
Vol 15 (10) ◽  
pp. 155014771988135
Author(s):  
Yanchao Yue ◽  
Tangbing Chen ◽  
Yongtao Bai ◽  
Xiaoming Lu ◽  
Yan Wang ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Seismic Design ◽  
Design Method ◽  
Performance Criteria ◽  
Main Beam ◽  
Frame Structures ◽  
Concrete Frame ◽  
Buckling Restrained Brace ◽  
Buckling Restrained Braces ◽  
Line Design

Buckling-restrained braces play a critical role as the first-defendant line in dissipating seismic energy and are often used in concrete frame structures to ensure that the main beam–column members are “undamaged” or significantly elastic during medium earthquakes. The design of the reinforced concrete frame structures with buckling-restrained brace is generally based on the assumption of shear deformation of the structure. The conventional seismic design considers the “second-defendant line design” based on the geometric relationship between the axial deformation and strength of buckling-restrained braces and stratified deformation. This article proposes iterative optimization of the buckling-restrained brace design method and layout scheme based on the nonlinear structural response of the calibrated numerical model, and then approximates the nonlinear structure scheme using a linear method. Time history analyses are performed to prove that the linear design method is highly conservative for estimating seismic intensity, and the proposed design method provides more efficient damage distributions in frame components. The results of the nonlinear performance evaluation and energy analysis indicate that the method proposed in this article can meet the performance design requirements achieving multi-performance criteria.

Development US Navy Gas Turbine Vibration Analysis Expertise: LM2500 Vibration and Trim Balance

2012 ◽  
Author(s):  
Bruce D. Thompson ◽  
Jurie Grobler
Keyword(s):  
Gas Turbine ◽  
Turbine Rotor ◽  
Gas Generator ◽  
Engine Operation ◽  
Engine Design ◽  
Power Turbine ◽  
Us Navy ◽  
Continued Use ◽  
Integrated Performance ◽  
Mean Time

Although generally reliable in-service and with an ever increasing mean time between removal, it was identified in the mid to late 1980’s that the LM2500 gas turbine in US Navy service had a problem with self generated vibration; this was principally due to imbalance in the gas generator or power turbine rotor, however, other non-synchronous sources for vibration were discovered to be important as well. The initial method for resolving this problem was to remove and repair, at a depot, the engines that exceeded the in-service alarm level. This turned out to be a very expensive approach and it was found that most engines that had excessive vibration levels in other respects (performance, etc.) were perfectly acceptable for continued use without repair. Raising the vibration alarm level was tried for a time. However, it became clear that prolonged engine operation with higher levels of vibration were detrimental to the mechanical integrity of the engine. This paper discusses the systematic approach developed to reduce LM2500 self generated vibration levels. This included monitoring system improvements, engine design & hardware improvements and the development and implementation of in-place trim balance. This paper also discusses some of the analysis and practical difficulties encountered reducing and maintaining low LM2500 vibration levels through trim balance and by other means. Also discussed is the present implementation of remotely monitoring LM2500 operating parameters, in particular vibration, through the Integrated Performance Analysis Reports (IPAR) and the Maintenance Engineering Library Server (MELS).

Paper 5: Compact Long-Life Diesel Engine

1968 ◽  
Vol 183 (2) ◽  
pp. 52-60 ◽  
Author(s):  
S. G. Timoney
Keyword(s):  
Diesel Engine ◽  
Service Life ◽  
Compression Ratio ◽  
Current Status ◽  
Engine Operation ◽  
Variable Compression Ratio ◽  
Specific Output ◽  
Air Supply ◽  
Operation Results ◽  
Variable Compression

Continued development work at University College, Dublin, on the variable compression ratio, two-stroke diesel engine, discussed in earlier communications to the Institution, has demonstrated the ability of this unique design to combine long service life with high specific output. The present paper summarizes the current status of the programme after four years' work. The basic design philosophy adopts a two-stroke cycle and exhaust gas turbocharging to obtain high specific output, and an automatic variable compression ratio mechanism to ensure long service life by controlling piston loads. The paper gives details of the variable compression ratio mechanism including the specification of the various components of which it is comprised. Test results show the response rate of the mechanism relative to changes in engine operation. Results are also given for the engine as operated with various air supply blowers to give characteristics suitable for specific user applications.

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