Reduced Part Count Research Articles

Initial Investigations into the Benefits and Challenges of Eliminating Port Overlap in Wankel Rotary Engines

<div class="section abstract"><div class="htmlview paragraph">The Wankel rotary engine historically found limited success in automotive applications due in part to poor combustion efficiency and challenges around emissions. This is despite its significant advantages in terms of power density, compactness, vibrationless operation, and reduced parts count in relation to the 4-stroke reciprocating engine, which is now-dominant in the automotive market. A large part of the reason for the poor fuel economy and high hydrocarbon emissions of the Wankel engine is that there is a very significant amount of overlap when the ports are opened and/or closed by the rotor apices (so-called peripheral ports). This paper investigates the benefits of zero overlap from a production engine with this characteristic and the effect of configuring a peripherally-ported Wankel engine in such a manner. As discussed in the paper, arranging this condition for peripherally-ported engines unfortunately reduces the trapped compression and/or expansion ratios significantly, such that when naturally-aspirated operation is simulated, a large reduction in performance ensues.</div><div class="htmlview paragraph">In order to demonstrate the potential of zero port overlap in Wankel engines with respect to emissions, a 2007 model year Mazda RX-8 was rebuilt, run-in, degreened, and tested on a chassis dynamometer. As standard, the engine in this vehicle is configured with no port overlap through the adoption of side intake and exhaust ports. This testing was performed in order to see subjectively how successful such an approach could be in controlling emissions. The vehicle easily met Euro 5 limits for all criteria emissions and was even better in terms of hydrocarbon emissions versus Euro 6 on the WLTP cycle, giving the lie to the belief that a Wankel engine can no longer meet current automotive emissions targets.</div><div class="htmlview paragraph">The analytical work reported here studies the result of eliminating overlap on the performance of a peripherally-ported single-rotor Wankel engine using a 1-D model. This was implemented and correlated to the in-production Advanced Innovative Engineering (UK) Ltd 225CS engine used in the UK government-funded ADAPT project. The initial port study focused on advancing and retarding the exhaust and intake port respectively to achieve zero port overlap and then sweeping their zero-overlap positions together around the trochoid housing. The best location for the ports was then identified; this was essentially an “Otto” timing set, with broadly equal compression and expansion ratios. Notwithstanding this, potential performance was found to be severely curtailed, as was to be expected given the marked reduction in trapped compression and/or expansion ratios necessary due to peripheral porting.</div><div class="htmlview paragraph">Countermeasures to this reduction are discussed. Those that will be studied later in the project will be reported in a later publication.</div></div>

A Capacitor Voltage Balancing Scheme for Single-Source Fed Switch Optimized Three-Phase Nine-Level Inverter

This article proposes a novel floating capacitor (FC) and dc-link capacitor voltage balancing scheme for a single-source three-phase nine-level inverter with reduced part count. Although nine levels are generated by keeping the dc-link capacitor voltage to FC voltage ratio as 3:1, it comes with complete absence of any useful pole voltage redundancies. Therefore, the conventionally adopted redundant-state-switching-based pulsewidth modulation technique cannot be applied for FC voltage balancing. Hence, a novel carrier-based modulation scheme is proposed here, which addresses the issue of FC voltage balancing by safely clamping the modulating reference to pole voltage levels that aid in FC voltage balancing. The dc-link capacitor voltages are also balanced using a unique way suitable for this inverter having nonredundant characteristics. Simulation and experimental results verify the capability of the proposed balancing scheme for the optimized nine-level inverter under different modulation and load conditions. It is found that a maximum fundamental phase peak voltage of 0.607 times dc-link voltage (at 0.91 modulation index) can be achieved at unity power factor and, thus, utilizing the dc bus of the inverter effectively.

Editorial on Special Issue “Fatigue and Fracture Behaviour of Additive Manufacturing Mechanical Components”

This Special Issue presents the latest advances in the field of fatigue and fracture performances of additively manufactured mechanical components, including components made of traditional materials (metals, sintered steels, etc.) but undergoing complex loading conditions (multiaxial fatigue and mixed mode fracture). This Special Issue is composed of seven papers covering new insights in structural and material engineering. The advent of additive manufacturing (AM) processes applied to the fabrication of structural components creates the need for design methodologies and structural optimization approaches that take into account the specific characteristics of the process. While AM processes give unprecedented geometrical design freedom, which can result in significant reductions of component weight (e.g., through part count reduction), they have implications in the fatigue and fracture strength due to residual stresses and microstructural features. This is due to stress concentration effects and anisotropy that still need research. The papers of this Special Issue report on numerical simulation and experimental work, or a combination of both. The application of damage and fracture mechanics concepts, the appraisal of stress concentration effects, and the consideration of residual stresses and anisotropic behaviour are tackled for a range of structural applications from biomedical engineering to aerospace components.

Closed-Loop Control and Performance Evaluation of Reduced Part Count Multilevel Inverter Interfacing Grid-Connected PV System

Multilevel inverters (MLIs) have drawn tremendous attention in the power sector. Application of MLI has grown extensively to improve the power quality and efficiency of the photovoltaic (PV) system. For an MLI interfacing PV system, the size, cost and voltage stress are the key constraints of the MLI that need to be minimized. This paper presents a novel reduced part count MLI interfacing single-stage grid-tied PV system along with a closed-loop control strategy. The proposed MLI consists of n repeating units and a level boosting circuit (LBC) that assists in generating 4n + 7 voltage levels instead of 2n + 3 levels. Three different algorithms are proposed for a proper selection of dc-link voltages to enhance the levels further. A comparative analysis is carried out to confirm the superiority of the developed MLI. The workability of the proposed MLI is investigated with a 1.3 kW PV system. The closed-loop control strategy ensures the maximum power tracking, dc-link voltage balancing, satisfactory operation of the MLI and injection of clean sinusoidal grid current under any dynamic changes. Comprehensive simulation analysis is carried out considering a 15-level MLI structure. Experimental tests further confirm the practicality of the topological advancement for a PV system under different dynamic conditions.

Performance Examination of SEPIC Based Hybrid Cascaded Single-Phase Multilevel Inverter

In the present scenario, reduced part count(RPC) multilevel inverters are become popular compared to traditional multilevel inverters(MLIs). This is mainly due to reduced size and cost and alleviates the issues of more passive components, flying capacitor voltage balancing issues and the requirement of complex switching schemes. Also, the RPC is getting attraction for various industrial and transportation applications. Therefore, in this paper, a novel 17 level inverter is proposed by cascading MLIs with the reduced part count. The complete operation, switching schemes and output are presented to evolve the performance under steady-state conditions using MATLAB software.

Interleaved centre clamped forward converter (ICCFC) for wide input voltage range applications

A new interleaved centre clamped forward converter for high current applications is proposed. It is a series input and series output structure with common active clamp reset branch. In the proposed converter, both the high input voltage stress and output current stress are reduced. The converter comprises of two active clamp forward converters with one common centre clamp reset circuit and the series output comprises of a current double rectifier (CDR) with self-driven synchronous rectifier (SDSR). The capacitor divider at the input reduces the switching stress due to input voltage. The common centre clamp circuit enables the transformer core reset without any additional circuit and enables zero volt switching. The SDSR-based CDR reduces burden on the secondary side of the transformer by an additional current sharing. Extended duty cycle beyond 50% is achieved. Overall reduction in the size of magnetic components with reduced part count and high-power density is attained. Prototype for 50 W with input voltage in the range of 50—200 V, 5 V/10 A output at 100 kHz was developed. The experimental results match the theoretical investigations.

Design, analysis and fabrication of thick co-cured wing structures

Over the past few decades advances in the design, materials, and manufacturing of thermoset composite materials have expanded rapidly. Nonetheless, aerospace structures have not yet adapted many of these technologies. This can be attributed to the risk adverse nature of the engineering community and associated regulatory agencies in this field.One of the technologies that has recently gained more traction in the composites field is the use of unitized co-cure structures. Driving this change is the potential for reducing part count, touch time and labor costs. Most of the work done to date focuses on thinner structures (~0.15 inch in thickness) resulting in a lack of understanding of the behavior of much thicker parts representing wing-like structures.This paper provides insight into the fabrication of a full-scale wing demo made from Cycom 5320–1. The design, analysis and fabrication aspects are discussed and presented. It was shown that utilizing an outer mold line (OML) tooling approach with silicon mandrels provided a final product that achieves the set engineering tolerances. Nondestructive inspection showed no defects or anomalies in the part using the proposed fabrication approach. In addition, a brief discussion on the part warpage was presented and concluded that the amount of warpage detected in thick co-cured structures is less than that observed in co-bonded and secondary bonded parts.

Forward Dual-Active-Bridge Solid-State Transformer for a SiC-Based Cascaded Multilevel Converter Cell in Solar Applications

Central inverters based on conventional topologies are the current preferred solution in solar farms because of their low cost and simplicity. However, such topologies have some disadvantages such as poor maximum power tracking, use of bulky filters, and low-frequency transformers. An interesting alternative in this case is the SiC-based cascaded multilevel converter (CMC), which provides a distributed maximum power point tracking control with reduced footprint and high flexibility. Each cell of a CMC usually has, as an intermediate stage, a solid-state transformer based on a dual-active-bridge dc–dc converter. Due to the unidirectional power flow characteristic of the photovoltaic application and aiming at further reduction in the converter volume, this work proposes a forward dual-active-bridge (F-DAB) topology, which reduces the number of active switches. This paper shows through analytical, simulation, and experimental results that the cell using an F-DAB is superior to other unidirectional topologies in three aspects: higher power density with commercially available power modules, reduced part count, and simplicity of control.

DFAM Based Multi-Material 3D Printing Using Conductive and Flexible Filaments

The focus of this study was to test a low-cost level plastic printer in the multi-material printing application using principles of design for additive manufacturing (DFAM). Two sample structures were designed in the project. One of the main planning principles of the examples was to integrate multiple functions into one part and intelligently utilize a variety of materials and reduce parts count. The most common material used in the experiments was the basic PLA, which is widely used, easy-to-print and economical alternative. As special materials, electrically conductive PLA-based graphene filament and highly flexible polyurethane-based filament was used. The results show that multi-material printing is also possible with lower cost devices and it makes it easier for smart products to be manufactured cost-effectively. It has also been found that multi-material printing can be technically challenging and that further research and experiments in this subject are needed. In the future, the research topic will be even more interesting as equipment and materials will develop. This paper presents detailed printing parameters for all the materials used in the printing tests.

Fabrication of Split-Section X-band Structure Using Elastic Averaging

Conventional accelerator structures are manufactured using axial stacks of cylindrical components which, when brazed together, form the accelerator cell structure. Splitting the accelerator structure into two sections along the beam axis allows for a significant reduction in part count and vacuum joint length [1]. The resultant single and coplanar vacuum joint between the two split sections allows for joining techniques such as electron beam welding or brazing of the parts to form the accelerator vacuum envelope. High precision alignment of the two sections is achieved through an elastic averaging interface coupling where improved accuracy is derived from the averaging of errors over a large number of relatively compliant contacting members. The monoblock split sections allow for highly optimized cooling configurations with enhanced heat removal in high heat flux regions, reducing vacuum wall thermal stresses and enabling higher power operation. This paper describes the engineering and manufacturing of four generations of brazed and electron beam welded Xband accelerator structures at both 9.3 GHz and 11.4 GHz frequencies.

Operation and Control of a Nine-Level Modified ANPC Inverter Topology With Reduced Part Count for Grid-Connected Applications

This paper presents a nine-level active-neutral-point-clamped (ANPC) based multilevel inverter (MLI) topology for grid-connected applications requiring only ten switches. The envisaged structure comprises two parts, namely five-level ANPC unit, and a two-level converter leg whose midpoint is used as another ac terminal. An ad hoc switching state redundancy based modulation strategy is used to ensure that the voltage across the flying capacitor is tightly balanced and is implemented using a look-up table further simplifies the control complexity. The performance and effectiveness of the proposed topology with its control scheme are validated through simulations and experimental tests. Comparison with other MLIs is included to highlight the merits of the proposed topology. From the results, it will be shown that the proposed inverter requires the least part count as compared to other topologies with the same performance and output quality.

Additive Manufacturing-Enabled Part Count Reduction: A Lifecycle Perspective

Part count reduction (PCR) is one of the typical motivations for using additive manufacturing (AM) processes. However, the implications and trade-offs of employing AM for PCR are not well understood. The deficits are mainly reflected in two aspects: (1) lifecycle-effect analysis of PCR is rare and scattered; (2) current PCR rules lack full consideration of AM capabilities and constraints. To fill these gaps, this paper first summarizes the main effect of general PCR (G-PCR) on lifecycle activities to make designers aware of potential benefits and risks and discusses in a point-to-point fashion the new opportunities and challenges presented by AM-enabled PCR (AM-PCR). Second, a new set of design rules and principles are proposed to support potential candidate detection for AM-PCR. Third, a dual-level screening and refinement design framework is presented aiming at finding the optimal combination of AM-PCR candidates. In this framework, the first level down-samples combinatory space based on the proposed new rules while the second one exhausts and refines each feasible solution via design optimization. A case study of a motorcycle steering assembly is considered to demonstrate the effectiveness of the proposed design rules and framework. In the end, possible challenges and limitations of the presented design framework are discussed.

State of the Art and Emerging Trends in Additive Manufacturing: From Multi-Material processes to 3D printed Electronics

Additive manufacturing is considered a disruptive technology that is expected to revolutionize production technology and affect value chains on a global scale. The scope of accessible materials ranges from polymers to metals and ceramics as well as composites. The keynote will provide an overview of available manufacturing processes for the various material groups and discuss the specific advantages of additive manufacturing – e.g. realization of complex geometries, part count and assembly effort reduction, art-to-part approach - in view of selected applications and production scenarios. Further to this, selected emerging trends in additive manufacturing will be presented and discussed, including fabrication of composites, hybrid structures, multi-material techniques and associated promises with respect to local tailoring of material properties, and the integration of sensors and/or electronic systems in AM parts.

How Practical is 3-D Metal Printing?

This article explores the application of 3D printing technology in cost-sensitive industries such as consumer products and power systems. Metal printing offers advantages such as the ability to reduce parts count, assembly time, and weight while creating complex internal and external geometries that could not be made any other way to manufacturers in almost every industry. 3D design also makes it possible to customize medical and dental implants for each patient. Industrial product designer Keith Handy used the flexibility of 3D printing to redesign the system. Instead of putting the device above the chain, he built a tunnel-like part that the chain could pass through. Euro-K, a Berlin-based firm that develops small energy converters, created a burner that could do both. 3D printing enabled Euro-K to optimize the burner’s geometry to handle gaseous fuels and difficult-to-burn liquids like fuel oils, a byproduct of alcohol distillation, while reducing size. The article concludes that as new competitors enter the 3D printing arena, systems will grow better, faster, and less expensive. In addition, most important of all, engineers will be standing by with lots of new and surprising ways to take advantage of 3D metal technology

Design, Fabrication and Performance Analysis of a Two Input—Single Output DC-DC Converter

A novel modified bridge-type dual input DC-DC converter, which is proficient for integrating distinct V-I characteristic sources such as solar-PV, wind, etc., and storages including battery, ultracapacitor, fuel cell, etc., is proposed in this paper. Three modes of operations such as boost, buck, and buck-boost are possible using the same structure of the converter, and the converter can operate even with the failure of any one of the input energy sources to deliver power to the load. A software simulation and experimental realization of the converter have been carried out for the buck, boost, and buck-boost operations. The voltage and current stress analysis of the power switches available in the converter have been carried out for the better selection of power switches. A simple power control strategy is proposed for the steady state, and dynamic performance analysis of the converter and performance comparison with existing converter topologies have been carried out based on the different parameters like duty ratio, efficiency, etc. The performance comparison shows that the proposed converter has high voltage gain, low voltage stress, reduced part counts and high efficiency.

Comparison of Reduced Part Count Multilevel Inverters (RPC-MLIs) for Grid Interfacing

ABSTRACTRecently, multilevel inverter (MLI) is gaining immense popularity due to reduced total harmonic distortion, lower electromagnetic interference, and high quality output waveform in high/medium voltage applications. The reduced part count (RPC)-MLI has attracted the researchers by providing higher number of output voltage level with reduced part count as compared to the classical topologies (cascaded H-bridge, neutral point clamped, and flying capacitor). But the discussion over their suitability for particular application is not yet explored completely. In this paper, some of the recently proposed RPC-MLI topologies are reviewed and analysed. RPC-MLI topologies are compared on the basis of number of switches, driver circuits, diodes, standing/blocking voltage across the switches, and switching losses for grid interfacing application. These topologies are simulated here under the same load and input source condition using real time simulator.

Design and Implementation of a Sensorless Multilevel Inverter With Reduced Part Count

This letter proposes a single-phase nine-level (9L) inverter topology suitable for grid-connected renewable energy systems. The proposed inverter is realized using a T-type neutral-point-clamped inverter connected in cascade to a floating capacitor (FC) H-bridge. Additionally, two low-frequency switches are added across the dc-link enabling the inverter to generate a 9L waveform. A sensorless voltage control based on redundant switching state is developed and embedded with PWM controller, which is responsible for regulating the FC voltage at one-quarter of the dc source voltage. The proposed PWM technique employs the generation of 9L waveform without using any voltage sensor, thereby reducing the complexity of the overall control scheme. This, in turn, will make the overall system appealing for various industrial applications. In comparison to conventional and recent topologies, generation of the 9L waveform using a lower number of components is the notable contribution. Another important feature of the proposed inverter is that if FC H-bridge fails, it can be bypassed, and the inverter can still operate as a 5L inverter at its nominal power rating. Furthermore, a comprehensive comparison study is included which confirms the merits of the proposed inverter against those of other state-of-the-art topologies. Finally, simulation and experimental results are included for validating the feasibility of the proposed system.

Topological Comparison of Dual-Input DC-DC Converters

Dual input dc-dc converters have two input voltage sources or one input source and an energy storage system like ultra capacitor, PV, battery, super capacitors and a single output load. In order to process the power in hybrid energy systems using reduced part count, researchers have proposed several multi-input dc-dc power converter topologies to transfer power from different input voltage sources to the output. This paper compares non-isolated dual-input converter topologies topologically ,based on the components count, various fields of application and different modes of operation for hybrid systems mainly used in electric vehicles and renewable energy systems composed of energy storage systems (ESSs) with different voltage-current characteristics. Dual input dc-dc converter topologies considered in this paper are investigated using MATLAB and PSIM software and output voltage and inductor current waveforms are shown.

A generic FPGA-based PWM generator with automatic device fault recovery for fuel cell, interleaved, multi-phase and multi-switch DC/DC boost converters

This paper describes the simulation and implementation of a generic FPGA-based PWM generator with automatic device fault recovery. This PWM generator is applied to multi-switch DC/DC boost converters for fuel cell applications; these converters have gained attention due to its reliability, equally-distributed power losses and reduced part count. In this paper, three different driving schemes for one phase and different legs are described and one driving scheme has been finally chosen. The operation of the proposed PWM generator with simulations and experimental results are shown. This PWM generator with automatic fault recovery, brings more reliability and fault robustness to fuel cell boost converters, making suitable to use in electric vehicle and uninterruptible power supplies (UPS). The method used in the PWM generator described on this paper, allows to change the number of devices working in DC/DC conversion, increasing the switching frequency and the duty cycle of the power switches, ensuring a DC/DC conversion without interruption.

A Bidirectional Nonisolated Multi-Input DC–DC Converter for Hybrid Energy Storage Systems in Electric Vehicles

To process the power in hybrid energy systems using a reduced part count, researchers have proposed several multiinput dc–dc power converter topologies to transfer power from different input voltage sources to the output. This paper proposes a novel bidirectional nonisolated multi-input converter (MIC) topology for hybrid systems to be used in electric vehicles composed of energy storage systems (ESSs) with different electrical characteristics. The proposed converter has the ability to control the power of ESSs by allowing active power sharing. The voltage levels of utilized ESSs can be higher or lower than the output voltage. The inductors of the converter are connected to a single switch; therefore, the converter requires only one extra active switch for each input, unlike its counterparts, hence resulting in reduced element count. The proposed MIC topology is compared with its counterparts concerning various parameters. It is analyzed in detail, and then, this analysis is validated by simulation and through a 1-kW prototype based on a battery/ultracapacitor hybrid ESS.