Torque Improvement Research Articles

Effect of Nitromethane Addition on the Performance of Two-Stroke Spark Ignition Unmanned Aerial Vehicles Piston Engine

Abstract Nitromethane has a stoichiometric air–fuel ratio of 1.7, which is 8.5 times lower than gasoline. For the same amount of air being drawn by the engine, more amount of nitromethane blends and hence more energy can be added. Methanol was used as a medium to mix nitromethane and gasoline, which are normally immiscible. Engine performance tests were carried out to study the effect of nitromethane addition to the methanol-gasoline blend. A large rise in engine torque and brake thermal efficiency (BTE) was obtained during the investigation. However, the brake specific fuel consumption (BSFC) also increased for the nitromethane blends. The engine parameters like spark timing, equivalence ratio, and compression ratio were optimized to further increase the engine power and also bring down the BSFC. A net torque improvement of 42%, BTE improvement of 35%, and BSFC rise of 9% were obtained by adding nitromethane and methanol in small fractions to gasoline. Combustion analysis was carried out using the cylinder pressure trace. High heat release rate and shorter combustion duration with nitromethane addition were observed. Emission measurements showed decrease in HC and CO emissions with nitromethane addition. However, a drastic rise in NO emissions was observed. Hence, it can be concluded that the specific power of small two-stroke spark ignition (SI) engines can be enhanced using nitromethane as a fuel additive to increase the payload of the unmanned aerial vehicles.

Performance improvement of direct torque controlled five‐phase induction motor in context of common‐mode voltage, torque ripple and demagnetisation under low speed region

This study focuses on the performance improvement of direct torque controlled (DTC) five-phase induction motor (FPIM). The performance indices are common-mode voltage (CMV), torque ripple and demagnetisation during low-speed operation. The three-level five-phase inverter (TL-FPI) is used for feeding the FPIM, since more voltage vectors are available in TL-FPI than its two-level counterpart. Among available 243 voltage vectors, 41 non-vertex voltage vectors are employed. These 41 voltage vectors through seven-level torque comparator (SLTC) fires an inverter. The SLTC reduces the torque ripple. All the employed 41 voltage vectors have zero CMV output. The voltage vectors are selected so that the magnitude of radial component of the resultant stator flux under low-speed operation is more than the same under normal speed operation. This modification resolves the problem of demagnetisation during low-speed operation. The proposed method achieves the intended targets without losing simplicity and dynamics of the classical DTC method. The performance improvement of the five-phase machine is validated through several results.

Torque ripples improvement of direct torque controlled five-phase induction motor drive using backstepping control

The paper proposes Direct Torque Control (DTC) of a five-phase induction motor drive with reduced torque ripple. The method presented here is the DTC Backstepping based on the classic DTC working with a constant switching frequency of the inverter. Another remarkable aspect is the complexity of the method proposed, both in the control unit of the inverter and in the number of correctors necessary for the control of the torque. The selection table and hysteresis have been eliminated. This method significantly improves the torque and flux oscillations and improves the dynamics of the drive by making it less sensitive to load torque disturbances. The proposed method is developed and designed using Matlab/SIMULINK to show the eectiveness and performances of the DTC-Backstepping.

Methods for Low Engine Speed Torque Improvement of Natural Gas Engine for Commercial Vehicles: Experimental Observations with Turbocharger and Supercharger

Diesel engines have been powering a range of commercial vehicles for a many years. Considering air pollution, there is a thrust on use of natural gas (NG). Thereafter, natural gas engines for commercial vehicles have been subject of development, particularly to meet drivability demands and emissions requirements.Bus used for intra-city mass transportation of passengers is probably the most common form of natural gas commercial vehicle. Considering typical city applications, such vehicles is characterized by low speeds, frequent gear changes, start-stops, traffic conditions etc. For better drivability, they need higher traction at low engine speeds. This study captures few means of torque enhancement and motive is to integrate a selective ones as not much research is available mentioning enhancements specifically at low engine speeds.Turbocharging of natural gas engine is complicated due to high exhaust temperatures. As most turbocharger manufacturers cater to requirements of diesel engine, turbochargers for natural gas are simply not available. Many compromises are thus to be made. Under this study, four different turbochargers and one supercharger shall be simulated for experimenting and optimizing to enhance torque at low engine speeds. A virtual model of reference, naturally aspirated engine is built in appropriate software and its output is verified against test bed performance, to establish model faithfulness. Next, simulation runs with different turbochargers and superchargers are carried out. Various parameters are recorded and compared. Findings are recorded and it is noted that there is room for enhancement based on different hardware capabilities.

Performance, combustion, and emission characteristics of a CI engine fueled with emulsified diesel-biodiesel blends at different water contents

Arising concerns over the energy crisis and ambient air pollution has motivated research into clean alternative fuels for use in internal combustion engines, from which it has been discovered that biodiesel can be used to partially replace fossilized fuels. However, the excess oxygen that is inherent in biodiesel causes an increase in the peak temperature during combustion, increasing NOx formation. The aim of this study is to investigate the effects of water emulsification on engine performance, combustion characteristics, and exhaust emissions. The experiment was carried out using conventional diesel, blended fuel B20, and B20 that has been emulsified with 5% water (B20E5), 10% water (B20E10), 20% water (B20E20), and 30% water (B20E30). Results indicate that a 28.4% improvement in the engine torque and a reduction of 7.27% BSFC was achieved using B20E5. A significant reduction from 52.1 to 46.4 bar was also observed in the peak in-cylinder pressure with B20E5. The 30% water content in the blended fuel B20 reduced the NOx emissions by as much as 26.17% compared to diesel fuel. Overall, the emulsification of biodiesel-diesel with water is found to be effective in tackling concerns about emissions, especially nitrogen oxides (NOx), with no penalty to engine performance.

Effect of Slot-Pole Combination on the Electromagnetic Performance of Ironless Stator AFPM Machine With Concentrated Windings

Due to the elimination of the magnetic core on the stator, the design of coils is more flexible and more sensitive to the number of rotor poles for ironless stator axial flux permanent magnet (AFPM) machine. The slot-pole combination is a vital aspect of optimization design for the improvement of torque and power density. This article is mainly aimed at investigating the influence of slot-pole combination on the comprehensive performance of ironless stator AFPM machine with non-overlapping concentrated windings. Firstly, the space utilization of coils and winding factor of non-overlapping concentrated winding are deduced in formula form to compare the output capacity. And the copper mass and utilization are analyzed with different numbers of slots and stator diameter. Then, field utilization ratio is defined and derived to analyze magnetic flux leakage of Halbach-array PM dual-rotor for different numbers of poles. The performance comparison of the optimized prototypes is carried out using three-dimensional finite element analysis (3-D FEA). The back-EMF, torque and winding loss are also highlighted. Finally, a 50 kW prototype with 12-slot and 10-pole is designed and manufactured for experimental validations. This paper provides a valuable reference to select the basic configuration for the ironless stator AFPM machine application.

Development of spoke-type IPM magnetic gear

Magnetic gears can change output-torque and -speed without any mechanical contacts. Therefore, they have a low acoustic noise and vibration, and their maintainability and reliability are high. Especially, a flux-modulated type magnetic gear is expected to be put into practical use because its torque density is higher than that of other magnetic gears. For the practical use, further improvement of torque and losses is important, especially, reduction of eddy current loss in permanent magnets (PMs) due to asynchronous harmonic magnetic fluxes is necessary. This paper investigates an interior permanent magnet (IPM) structure to improve the efficiency by reducing the eddy current loss in PMs. In addition, this paper presents a method for increasing torque of the IPM magnetic gear by changing a position of magnetic-bridge.

Analytical Prediction and Analysis of Electromagnetic-Thermal Fields in PM Eddy Current Couplings With Injected Harmonics Into Magnet Shape for Torque Improvement

To improve the output torque in permanent magnet (PM) eddy current couplings, a new structure based on harmonics injection into the magnet optimization theory is proposed. Then, a novel analytical electromagnetic-thermal model is established that can accurately reflect the 3-D distributions of the magnetic field and the eddy current. With the proposed analytical model, the eddy current loss, temperature distribution, torque characteristics and influence of the temperature rise caused by load increases on the torque are predicted and analyzed precisely. The maximum output torque can be improved by 11.22% with injected harmonics into the magnet shape. On this basis, an optimal design of the conductor plate structure is presented, based on the electromagnetic-thermal analytical model. An additional 13.05% torque improvement can be obtained, which leads to better torque characteristics and overload capability. Verification is conducted by a 3-D finite element analysis and measurements. The analytical model solves the multiphysics coupling analysis problem of PM eddy current couplings, and provides a fast and accurate calculation method to perform electromagnetic-thermal coupling analysis.

Multi-Component Exercise with High-Intensity, Free-Weight, Functional Resistance Training in Pre-Frail Females: A Quasi-Experimental, Pilot Study

BackgroundNo study has performed an exercise intervention that included high-intensity, free-weight, functional resistance training, and assessed frailty status as an inclusion criteria and outcome measure via original, standardized tools, in pre-frail females.ObjectivesDetermine if the intervention strategy is not only feasible and safe, but can also improve frailty status, functional task performance, and muscle strength.DesignPilot, quasi-experimental.SettingCommunity.Participants 20 older-adults with pre-frailty characteristicsIntervention12-weeks (3 days/week, 45–60 minutes/session) of multi-component exercise, inclusive of aerobic, resistance, balance and flexibility exercises. The crux of the program was balance and resistance exercises, the latter utilized high-intensity, free-weight, functional resistance training. The control group maintained their usual care.MeasurementsFeasibility and safety (dropout, adherence, and adverse event)Frailty (Frailty Phenotype, Clinical Frailty Scale, and gait speed)Functional task performance (grip strength and sit-to-stand time); andIsometric and isotonic strength of the knee extensors and elbow flexors.ResultsNo participants dropped out of the intervention or experienced an adverse event, and adherence averaged 88.3%. The exercise group became less frail, whereas the control group became more frail. There was a significant within-group improvement in exercise participants gait speed (p ≤ 0.01, +0.24 m/sec), grip strength (p ≤ 0.01, +3.9 kg), and sit-to-stand time (p ≤ 0.01, -5.0 sec). There was a significant within-group improvement in exercise participants knee extension isometric torque (p ≤ 0.05, +7.4 Nm) and isotonic velocity (p = ≤ 0.01, +37.5 °/sec). Elbow flexion isotonic velocity significantly declined within the control group (p ≤ 0.01, -20.2 °/sec) and demonstrated a significant between-group difference (p ≤ 0.05, 40.73 °/sec) post-intervention.ConclusionsThe intervention strategy appears to be feasible and safe, and may also improve frailty status, functional task performance, and muscle strength. These results help calculate effect size for a future randomized controlled trial.

Effect of a strength or hypertrophy training protocol, each performed using two different modes of resistance, on biomechanical, biochemical and anthropometric parameters.

The study aimed to analyse the effectiveness of two variants of 8-week strength training (hypertrophy, strength) with different modes of resistance. Healthy male subjects (n=75) were allocated to five groups of equal size: hypertrophy training with a variable cam (Hyp-Cam), hypertrophy training with disc plates (Hyp-Disc), maximal strength training with a variable cam (Str-Cam), maximal strength training with disc plates (Str-Disc), and a control group (CG). The Hyp-Cam and Str-Cam groups trained with a machine where the load was adjusted to the strength capabilities of the elbow flexors. The Hyp-Disc and Str-Disc groups trained on a separate machine in which a load was applied with disc plates. The CG did not train. All groups were assessed for changes and differences in one-repetition (1RM) lifts, isokinetic muscle torque, arm circumference and arm skinfold thickness, and plasma creatine kinase (CK) activity. Within the 8-week training period the 1RM increased (p<.001) in all groups by over 20%, without significant between-group differences. Muscle torque increased significantly (p<.001) only in the Hyp-Cam group (by 13.7%). Arm circumference at rest increased by 1.7 cm (p<.001) and 1.1 cm (p<.001) in the Hyp-Cam and Hyp-Disc groups, respectively, but not in the Str-Cam (0.3 cm; p>.05) or Str-Disc (0.2 cm; p>.05) group. Skinfold thickness of the biceps and triceps decreased more within the 8-week period in Str-Cam (by 1.1 and 2.1 cm; p<.001 and p<.001 respectively) and Str-Disc (0.7 and 1.5 cm; p<.001 and p<.01 respectively) than in Hyp-Cam (by 0.4 and 1.8 cm; p>.05 and p<.01 respectively) and Hyp-Disc groups (by 0.2 and 1.4 cm; p>.05 and p<.05 respectively). CK activity was significantly (p<.05) elevated in each training group except Hyp-Cam (p>.05). The 8-week hypertrophy training with a variable cam results in greater peak muscle torque improvement than in the other examined protocols, with an insignificant increase in training-induced muscle damage indices.

Modulation Effects in an Inverter Fed Nine-Phase Induction Motor Drive

Using electric motors with a number of phases greater than three present some advantages over conventional three-phase machines: higher reliability, reduced power per phase, increased torque density, and reduced torque pulsations. As the number of phases increases, the complexity of the modulation also increases due to a larger number of switching vectors and harmonic planes. A nine-phase inverter implies 512 switching vectors in each one of its four harmonic planes. In this article, a modulation technique for a nine-phase inverter based on a subset of the voltage vectors that yields a reduced number of on/off transitions in a switching period is shown. The resulting harmonics and their effects in multiphase machines are analyzed. Third harmonic injection is considered from the perspective of both torque improvement and dc bus voltage utilization. Simulation, finite element, and experimental results are presented to support the authors’ conclusions.

Supination torque following single- versus double-incision repair of acute distal biceps tendon ruptures

Compared with single-incision (SI) distal biceps repair, double-incision (DI) repair has been described as permitting a more anatomic repair. We hypothesized that DI repair would result in greater terminal supination torque compared with SI repair for acute distal biceps ruptures. Patients were included if they sustained an isolated, acute distal biceps rupture repaired between January 2012 and December 2017. Isometric forearm supination torque in 4 positions wasmeasured using a validated uniaxial torque-testing device. Testing took place at least 12 months from surgery. The primary outcome was supination torque in the 60° supinated position. Secondary outcomes included supination torque in other forearm positions and functional outcome scores. The study included 37 patients: 15 underwent repair with the DI technique and 22 with the SI technique. The mean age was 47.3 years, the median follow-up time was 28.1 months, and demographic data were similar between cohorts. Mean supination torque, relative to the unaffected side, was 61% (95% confidence interval, 45%-77%) for DI repair vs. 80% (95% confidence interval, 69%-92%) for SI repair in the 60° supinated position (P = .036). In a multivariable linear regression model controlling for arm dominance, age, follow-up time, and workers' compensation status; SI repair was associated with greater mean supination torque than DI repair by 20% (P = .015). Contrary to our hypothesis, we found a 20% mean improvement in terminal supination torque for acute distal biceps ruptures repaired with the SI technique compared with the DI technique. This finding may have clinical significance for the more discerning, high-demand patient.

Optimal Stator Design of Doubly Salient Permanent Magnet Generator for Enhancing the Electromagnetic Performance

An optimal stator design technique of a three-phase doubly salient permanent magnet generator (DSPMG) for improving the output power is proposed. The stator configuration was optimally designed by adjusting the stator pole depth and stator pole arc. The trapezoid outer stator tip was also designed. Then, the output characteristics of the designed DSPMG including the flux linkage, electromotive force (EMF), harmonic, cogging torque, efficiency, magnetic flux distribution and voltage regulation were characterized by using the finite element method. Results were compared to the original structure in the literature. It was found that the flux linkage, EMF, cogging torque, and efficiency of the proposed DSPMG were significantly improved after the stator pole depth and stator pole arc were suitably modified. Further details of optimal stator pole depth and stator pole arc are presented. The EMF produced by the optimal proposed structure was 47% higher than that of the conventional structure, while 56% cogging torque improvement and 20% increased efficiency were achieved. The EMF generated by the proposed structure was classified in the high-range scale compared to the other existing models. The symmetrical magnetic flux distribution of all structures was indicated. The voltage regulation of the modified structure was also significantly improved from the conventional model. The proposed design technique can be utilized to maximize the electromagnetic performance of this particular generator type.

An experimental study on optimal spark timing control for improved performance of a flex fuel vehicle engine

In the American continent, the most frequently used alternative fuel is ethanol. Especially in Brazil, various blends of gasoline–ethanol fuels are widely spread. The vehicle using blended fuel is called flexible fuel vehicle. Because of several selections for the blending ratios in gas stations, the fuel properties may vary after refueling depending on a driver’s selection. Also, the combustion characteristics of the flexible fuel vehicle engine may change. In order to respond to the flexible fuel vehicle market in Brazil, a study on blended fuels is performed. The main purpose of this study is to enhance performance of the flexible fuel vehicle engine to target Brazilian market. Therefore, we investigated combustion characteristics and optimal spark timings of the blended fuels with various blending ratios to improve the performance of the flexible fuel vehicle engine. As a tool for prediction of the optimal spark timing for the 1.6L flexible fuel vehicle engine, the empirical equation was suggested. The validity of the equation was investigated by comparing the predicted optimal spark timings with the stock spark timings through engine tests. When the stock spark timings of E0 and E100 were optimal, the empirical equation predicted the actual optimal spark timings for blended fuels with a good accuracy. In all conditions, by optimizing spark timing control, performance was improved. Especially, torque improvements of E30 and E50 fuels were 5.4% and 1.8%, respectively, without affecting combustion stability. From these results, it was concluded that the linear interpolation method is not suitable for flexible fuel vehicle engine control. Instead of linear interpolation method, optimal spark timing which reflects specific octane numbers of gasoline–ethanol blended fuels should be applied to maximize performance of the flexible fuel vehicle engine. The results of this study are expected to save the effort required for engine calibration when developing new flexible fuel vehicle engines and to be used as a basic strategy to improve the performance of other flexible fuel vehicle engines.

Anatomical and Neuromuscular Determinants of Strength Change in Previously Untrained Men Following Heavy Strength Training.

This study examined whether changes in strength following a moderate-duration strength training program were associated with changes in specific combinations of anatomical and neuromuscular variables. 36 men (18–40 y) completed 10 weeks of lower-limb heavy resistance (6-RM) strength training. Measurements included cross-sectional area (CSA), fascicle length (lf) and fascicle angle (θf) from proximal, middle and distal regions of the four quadriceps components; agonist (EMG:M), antagonist (EMG) muscle activities and percent voluntary quadriceps activation (%VA; interpolated twitch technique); patellar tendon moment arm distance; and maximal isometric, concentric and eccentric (60° s–1) torque. Multiple regression models were developed to quantify the relationship between the change in maximum torque and the changes in combinations of anatomical and neuromuscular variables. The best model for each contraction mode was determined using Akaike’s Information Criterion (AICc), an information-theoretic approach for model selection. Strength increased significantly following training (mean range = 12.5–17.2%), and moderate relationships were observed between modeled data (using best-fit prediction models) and the change in torque for each contraction mode. The change in isometric torque was best (although weakly) predicted by the linear combination of the change in proximal-region vastus lateralis (VL) CSA and fascicle angle (R2 = 0.27, p < 0.05; AICcwi = 0.52, i.e., the probability the model would be selected as the “best model”). The models best predicting the change in concentric and eccentric torque both included the combination of the change in quadriceps (i.e., mean of all muscles) EMG:M and the change in vastus intermedius fascicle angle combined with either a change in proximal-region VL (R2 = 0.40, p < 0.001; AICcwi = 0.15) or whole quadriceps (R2 = 0.41, p < 0.001; AICcwi = 0.30) CSA (concentric and eccentric, respectively). Models incorporating the change in proximal CSA typically received substantial support (AICC < 2) for concentric torque prediction models, and the change in % VA and pre-training moment arm distance had substantial support for use in eccentric torque prediction models. In conclusion, adaptations varied between individuals, however strength training programs targeted to improve a group of variables that particularly includes agonist muscle activation might yield the greatest improvements in concentric and eccentric knee extension strength, whereas proximal muscle size and fascicle angle appear most important for isometric torque improvements.

Experimental investigation of four stroke single cylinder SI engine by modified intake manifold by using computational fluid dynamics

The research reveals that the optimisation of an intake manifold plays an important role in manifold design to maximise the quantity of air received into the cylinder for competent combustion. Traditional manufacturing of intake manifolds and the trial and error method to select an optimised manifold is time-consuming and cost-effective. This work focuses on the design of an intake manifold with different configuration such as normal, convergent and venture types and the study of the air flow through each designed manifolds has been performed using CFD. On comparison of the analysis results, an optimised intake manifold which allows maximum airflow inside the cylinder has been selected for efficient combustion. Experimental Studies on emission level reduction shows that the flow harnessing in the intake manifold of the IC engine can yield improvement in engine torque up to 10% along with a nominal decrease in emission level.

Postfault Zero-Sequence Current Injection for Open-Circuit Diode/Switch Failure in Open-End Winding PMSM Machines

This paper proposes and experimentally assesses two zero-sequence current control strategies that allow continuous operation of the three-phase dual-inverter drive using an open-end winding permanent magnet synchronous machine (PMSM) when freewheel diodes (or semiconductor switches) in either inverters fail open circuit. With an identified failure present, the proposed control strategies inject zero-sequence current to bias the phase current(s) of the faulted phase(s) such that the phase current(s) are unipolar, thereby eliminating current flow in the device(s) that have failed. Two possible injection modes are proposed. The first mode injects the minimum required zero-sequence current to bias the current in the phase that has a semiconductor open-circuit failure(s). The injected zero-sequence current varies over a fundamental cycle. This minimizes the increase in total rms currents in the phases yielding higher torque capability in fault conditions. The second mode injects a zero-sequence current that has a constant value over a fundamental cycle to bias all three-phase currents appropriately. This mode is used if more than one phase has suffered a fault. Additional thermal and current stresses resulting from both techniques were assessed and compared. A detailed electromagnetic torque model was also developed to demonstrate that the zero-sequence current does not affect the average torque output. Experimental results verify the theoretical treatment and are used to examine the advantages of techniques and show the improvement in the maximum available torque under fault conditions.

Design and Verification for the Torque Improvement of a Concentrated Flux-Type Synchronous Motor for Automotive Applications

In this paper, the design of the concentrated flux-type synchronous motor (CFSM) using ferrite permanent magnets to improve torque is proposed for an automotive chassis actuator. The thin pancake type CFSM of this paper has considerable axial magnetic leakage flux due to structural reasons. It is, therefore, necessary to improve the torque. In order to meet the required specifications in a constrained installation space, this paper proposes two methods for torque improvement. The first method is the alternate-stacking core as this structure removes the magnetic leakage flux path. The second method is the rotor overhang that increases the air-gap flux density. Furthermore, the structures require a three-dimensional (3-D) finite element method (FEM) analysis for accuracy. However, to analyze the characteristics easily and quickly, the 3-D structure is made into the equivalent 2-D FEM through an analytical method using an equivalent magnetic circuit. Finally, in this paper, the validity of the design process and the effectiveness for torque improvement is verified through experiments.

Trampoline Versus Resistance Training in Young Adults: Effects on Knee Muscles Strength and Balance

ABSTRACTPurpose: Trampoline parks are becoming popular in many countries, providing recreational facilities for children and adults. This study investigated the effects of trampoline training on knee muscles strength and balance in young adults. Methods: Twenty-six participants (14 males, 12 females) were randomized into trampoline training (TT) and resistance training (RT) groups to undergo a 6-week supervised intervention program (2 × 30 min per week). TT group performed basic trampoline exercises while the RT group performed resistance training targeting lower extremities muscles. Peak knee extension and flexion torque, postural sway characteristics, and Y balance test (YBT) performance were evaluated before and after the intervention. A mixed model analysis of variance (group × time) was applied. Results: After training there were significant improvements in knee extension torque (mean differencepost-pre [95% CI], TT: 0.27 [0.00, 0.54] N∙m/kg, RT: 0.31 [0.09,0.54] N∙m/kg, p = .001), knee flexion torque (TT: 0.25 [0.17,0.33] N∙m/kg, RT: 0.21 [0.08,0.34] N∙m/kg, p < .001), and dynamic balance (YBT composite scores, mean differencepost-pre [95% CI], TT: 4.9 [−0.3, 10.2]%, RT: 5.2 [2.4,8.0]%, p = .001). No difference between groups was found. Conclusion: Trampoline training can be as effective as resistance training for improving knee muscles strength and dynamic balance in young men and women.

Omega-3 Supplementation Does Not Impair Torque and Power Improvements Following 8 Weeks Eccentric Quadriceps Training

Omega-3 Supplementation Does Not Impair Torque and Power Improvements Following 8 Weeks Eccentric Quadriceps Training