Full Throttle Condition Research Articles

Influence of additive mixed ethanol-biodiesel blends on diesel engine characteristics

Automobile pollution has escalated the environmental degradation manifold, causing climate change. Numerous research works are being carried out to find alternative fuels that can improve efficiencies and limit emission levels. The present research work focuses on experimental investigation of DICI-VCR engine is performed to evaluate the performance and emission (PCE) characteristics using ethanol and Al2O3 nanoparticle blended biodiesel. Nine blends of biodiesel, diesel, and ethanol were prepared on v/v basis. Biodiesel was mixed in constant proportions and Al2O3 nanoparticles were added as additives in the blends with the proportion of 100 ppm. Physical and chemical properties were tested and found within the limits of ASTM D6751 and ASTM D975 standards. Experiments were conducted at constant compression ratio (18:1) with variable loading at full throttle condition. The study showed that the reduction in performance and emission characteristics such as brake thermal efficiency, mechanical efficiency, volumetric efficiency, carbon monoxide, and hydrocarbons ranges from 3.7% to 8.7%, 3.4% to 9.9%, 0.3% to 0.6%, 7.5% to 26.5%, and 8% to 27% respectively whereas increment in brake specific fuel consumption, exhaust gas temperature, carbon dioxide, and oxides of nitrogen as 4.5% to 22.4%, 0.9% to 4.8%, 17.5% to 43%, 4% to 9% respectively observed in comparison with neat diesel.

Energy and Exergy Analyses of Multiple Biodiesel Blended Diesel Engine

Abstract This paper deals with the experimental investigation of direct injection compression ignition (DICI) engine runs with multiple biodiesels–diesel blended and neat diesel fuels along with the energy-exergy analysis to evaluate quantitative and qualitative data for determining energy and exergy efficiencies, losses, and exergy destruction. Second-generation biodiesels are utilized to conduct experiments on engine with constant speed and full throttle condition at a compression ratio of 17.5:1. Energy analysis is based on experimental data, and exergy analysis is performed with the help of derived formula using chemical and molecular structures. Variation in the performance, combustion, and emission parameters for B0, B10, and B20 blends reveals that BTE, AFR, η(mech.), η(vol.), CP, and CO decrease with the increase in BSEC, EGT, MGT, RPR, NHR, CO2, HC, and NOx. Energy-exergy analysis shows that the combustion and exergetic efficiencies are maximum for the B20 blend (+87.73%) and (+52.04%) at 2.5 kW and 3.3 kW BPs. Exergy destructed is observed to be three-fifth of total available exergy. Half of the heat supplied is carried away by cooling water while one-third of heat is converted into brake power, and the remaining heat is lost in exhaust gases and unaccounted losses.

Performance assessment of multiple biodiesel blended diesel engine and NOx modeling using ANN

This paper discusses the effect of dual blends of multiple biodiesels on characteristics of DICI engine in conjunction with NOx modeling using ANN. Six sets of dual biodiesel/diesel blends are prepared on a volume basis (10% and 90%) by using four different biodiesels such as Jatropha, Karanja, Mahua, and Neem. The experimentations are performed on a single-cylinder VCR engine with full throttle condition and constant compression ratio (CR) of 17.5:1. The physicochemical and thermal properties are analysed to assess the suitability and compatibility of biodiesel as an alternative fuel. The physicochemical properties are found within the permissible limits as prescribed by ASTM. Mass loss study and functional groups are analysed through TGA and FTIR analysis and maximum weight loss is observed in pyrolytic zone (Zone-II). Reduction in performance characteristics of BTE, AFRηMech., ηVol. varies from −0.77% to −5.60%. Variations are observed in BSEC (8.91%) and EGT (11.95%). Combustion characteristics (CP, MGT, MFB, NHR, and RPR) of biodiesel blends are similar to neat diesel. Overall reduction in CO (34.05%) and increment in CO2 (42.54%) are observed for all the blends at the penalty of HC and NOx. An attempt has been made to predict NOx emission through physicochemical properties.

Experimental investigation for evaluating the performance and emission characteristics of DICI engine fueled with dual biodiesel-diesel blends of Jatropha, Karanja, Mahua, and Neem

The present research work focuses on evaluating performance, combustion and emission characteristics of DICI engine fueled with dual biodiesel blends. The study aims to examine the potential of application of dual biodiesel blends produced from non-edible category of bio-oils from Jatropha (Jatropha Carcus), Karanja (Pongamia Pinnata), Mahua (Madhuca Indica), and Neem (Azadirachta Indica). By using these four biodiesels, six sets of dual biodiesel blends are prepared (i.e. 10 % Biodiesel and 90 % Diesel). Based on the characterization study, it is found that physio-chemical properties are within permissible limits. Thermogravimetric Analysis (TGA) and Fourier Transform Infrared Spectroscopic (FTIR) analysis is conducted to examine thermal properties and functional groups of biodiesel blends under consideration. Performance parameters are evaluated for DICI engine at various engine loads with full throttle condition. The performance parameters such as air/fuel ratio, brake thermal, mechanical, and volumetric efficiencies are lower, whereas brake specific energy consumption (BSEC), and exhaust gas temperature (EGT) are higher compared to neat diesel. The effects of blends on exhaust emissions like CO, CO2, HC and NOx were investigated and compared with neat diesel. Blend D90 + JB5+NB5 indicates highest reduction in CO (46.91 %). All the blends under considerations shows higher CO2 emission compared to neat diesel.

Experimental assessment of lean-burn characteristics for a modified diesel engine operated in methanol direct injection spark ignition (DISI) mode at full throttle condition

In this study,the lean-burn characteristics of a high-compression direct injection spark ignition (DISI) methanol engine were investigated. The tests were conducted on a modified diesel engine in methanol DISI mode at three excess air ratios (1.2, 1.3, and 1.4) and injection timings from −60° to −300° crank angle (CA) after top dead center (ATDC). The engine was run at 1500 rpm, 100% throttle opening, and spark timing at maximum brake torque condition. The results demonstrated that the test engine under lean-burn condition can obtain the higher indicated thermal efficiency (ITE), but the lower indicated mean effective pressure (IMEP). The THC, CO, CO2 and NOX emissions are all reduced with the increased λ. Injection timing had a large influence on the combustion and emissions and these influences became largely in the case of retarded injection conditions. There existed an optimum injection timing of −240 °CA ATDC where the IMEP and ITE got their highest values along with the lowest coefficient of variation in indicated mean effective pressure (COVIMEP). Meanwhile, the THC and CO emissions are lowest, but the CO2 and NOX emissions highest. The methanol engine can obtain the maximum toque of 27.6 N·m, which is 25.3% more than the original diesel engine at the same speed. Meanwhile, there was no knocking throughout the entire experiment, and the maximum pressure rise rate and COVIMEP were found to be 0.4 MPa and 4.1%, and those are much less than the critical points of 1.0 MPa and 5%, respectively.

Comparative Analysis of a Four Stroke Spark Ignition Engine Performance Using Local Ethanol and Gasoline Blends

This paper presents performance of gasoline engine under locally produced ethanol blended with gasoline. A naturally aspirated four stroke single cylinder spark ignition engine test bed was used at various engine speeds. Different proportion of ethanol-gasoline blends were tested; E0 (0% ethanol and 100% gasoline), E1 (1% ethanol and 99% gasoline), E3 (3% ethanol and 97% gasoline) and E5 (5% ethanol and 95% gasoline). Using a sample size of 100, data were collected and analysed for all the fuel samples tested at different test conditions. The result showed improved engine performance with locally produced ethanol – gasoline blends. The maximum engine performance was attained by E3 at full load throttle condition. The local ethanol-gasoline blends gave a better engine performance over pure gasoline at different test condition. In conclusion, the study proved that locally produced ethanol can be used as a substitute to highly purified ethanol as additive in gasoline.

Evaluation of the engine performance and exhaust emissions of biodiesel-bioethanol-diesel blends using kernel-based extreme learning machine

It is known that biodiesel and bioethanol are viable alternative fuels to replace diesel for compression ignition engines. In this study, an experimental investigation is carried out to evaluate the performance and exhaust emissions of a single cylinder diesel engine fuelled with biodiesel-bioethanol-diesel blends. The engine performance parameters evaluated are the brake specific fuel consumption and brake thermal efficiency whereas the exhaust emission parameters evaluated are carbon monoxide, nitrogen oxide, and smoke opacity. Kernel-based extreme learning machine is used to predict the engine performance and exhaust emission parameters of the fuel blends at full throttle conditions. Based on the experimental results, the brake specific fuel consumption is lower while the brake thermal efficiency is higher for the biodiesel-bioethanol-diesel blends. The carbon monoxide emissions and smoke opacity are also lower for these fuel blends. The mean absolute percentage error of the brake specific fuel consumption, brake thermal efficiency, carbon monoxide, nitrogen oxide, and smoke opacity is 1.363, 1.482, 4.597, 2.224, and 2.090%, respectively. Thus, it can be concluded that K-ELM is a reliable method to estimate the engine performance and exhaust emission parameters of a single cylinder compression ignition engine fuelled with biodiesel-bioethanol-diesel blends to reduce fuel consumption and exhaust emissions.

Investigating the effect of MgO and CeO2 metal nanoparticle on the gasoline fuel properties: empirical modeling and process optimization by surface methodology.

The main purpose of this paper is to investigate how to optimize gasoline in order to reduce the emitted pollutants caused by combustion, while the torque and power of the engine reach the maximum capabilities. To optimize gasoline formulation, an ethanol and magnesium oxide (MgO) or cerium oxide (CeO2) mixture was added to gasoline. This study explores the role of main variables such as type of metal nanoparticle additive, engine speed, and throttle on engine performance and exhaust gas emissions through the modeling and optimization methods. Experimental design conducted through the implementation of D-optimal design, taking into account the three main parameters. To review the efficiency of this novel fuel, it was tested by a four-stroke engine connected to a dynamometer and an analyzer, under different controlled environments: speeds of 1500, 2000, 2500, and 3000rpm at both half and full throttle conditions. The analyzed data are the power and torque of the engine, the amount of emitted CO, CO2, HC, and NOx, the octane index, and the viscosity. The analyzed data were calculated and turned into models. Applying the models to data (the optimization process), close correlation between predicted and actual outcomes was found, highlighting the validity of the work. A secondary finding is that the CeO2 mixture used at higher speeds and throttles produces less emissions, while lower speeds and throttles using the MgO mixture produce less emissions.

Performance and emission characteristics of a spark ignition engine fuelled with butanol isomer-gasoline blends

The heavy reliance on petroleum-derived fuels such as gasoline in the transportation sector is one of the major causes of environmental pollution. For this reason, there is a critical need to develop cleaner alternative fuels. Butanol is an alcohol with four different isomers that can be blended with gasoline to produce cleaner alternative fuels because of their favourable physicochemical properties compared to ethanol. This study examined the effect of butanol isomer-gasoline blends on the performance and emission characteristics of a spark ignition engine. The butanol isomers; n-butanol, sec-butanol, tert-butanol and isobutanol are mixed with pure gasoline at a volume fraction of 20vol%, and the physicochemical properties of these blends are measured. Tests are conducted on a SI engine at full throttle condition within an engine speed range of 1000–5000rpm. The results show that there is a significant increase in the engine torque, brake power, brake specific fuel consumption and CO2 emissions with respect to those for pure gasoline. The butanol isomers-gasoline blends give slightly higher brake thermal efficiency and exhaust gas temperature than pure gasoline at higher engine speeds. The iBu20 blend (20vol% of isobutanol in gasoline) gives the highest engine torque, brake power and brake thermal efficiency among all of the blends tested in this study. The isobutanol and n-butanol blend results in the lowest CO and HC emissions, respectively. In addition, all of the butanol isomer-gasoline blends yield lower NO emissions except for the isobutanol-gasoline blend.

Effect of piston geometry on performance and emission characteristics of an LPG fuelled lean burn SI engine at full throttle condition

This paper investigates the influence of piston squish area in LPG fuelled lean burn Spark Ignition (SI) engine on performance, emissions, combustion and cyclic variation at constant speed. The piston squish area is varied by 25%, 30%, 35% and 40% of total piston area. A single cylinder diesel engine is modified to operate as SI engine at a compression ratio of 10:1 at 1500rpm. Tests are conducted at 100% throttle opening condition with different equivalence ratios under lean operation on different squish areas and results are analyzed. It is observed that the increase in squish area beyond 30% leads to instability in combustion towards lean equivalence limit. An appreciable increase in brake power and brake thermal efficiency is noticed in the equivalence ratios between 0.7 and 0.9 for 30% squish area piston. The HC emission level of 30% squish area piston is less compared to 25%, 35% and 40% squish area pistons. There is a noticeable increase in the NO emission in 30% and 25% squish area pistons compared to 35% and 40% squish area pistons. The investigations carried over suggest that 30% squish area piston is the most suitable for LPG fuelled lean burn SI engine.

Effect of Octane on Performance, Energy Consumption and Emissions of Two Euro 4 Passenger Cars

The combustion performance of gasoline engines has traditionally been measured using Research Octane Number (RON) and Motor Octane Number (MON) which describe antiknock performance under different conditions. Recent literature suggests that MON is less important than RON in modern cars and a relaxation in the MON specification could improve vehicle performance, while also helping refiners in the production of gasoline. At the same time, for the same octane number change, increasing RON appears to provide more benefit to engine power and acceleration than reducing MON. It has also been suggested that there could be fuel efficiency benefits (on a tank to wheels basis) for specially adapted engines, for example, operating at higher compression ratio, on very high RON (100+). Other workers have advocated the use of an octane index (OI) which incorporates both RON and MON to give an indication of octane quality.The objective of this study was to investigate the effect of RON and MON on the power and acceleration performance of modern gasoline vehicles under full throttle acceleration conditions. Tests were carried out using two Euro 4 vehicles. Fuels covering RON levels from 95 to 103 and sensitivities (RON minus MON) of up to 15 were blended. Both pure hydrocarbon and blends containing ethanol or ETBE were included so that specific effects of oxygenates could be identified. The results confirmed the findings of other studies that MON is not a good predictor of vehicle performance and in fact high MON levels increase acceleration time under full throttle conditions. In addition to performance testing, emissions testing was also carried out. Carbon balance was used to calculate energy consumption during the acceleration tests and NEDC tests.

Impacts of NOx reducing antioxidant additive on performance and emissions of a multi-cylinder diesel engine fueled with Jatropha biodiesel blends

Energy requirements are increasing rapidly due to fast industrialization and the increased number of vehicles on the road. The use of biodiesel in diesel engines instead of diesel results in the proven reduction of harmful exhaust emissions. However, most researchers have reported that they produce higher NOx emissions compared to diesel, which is a deterrent to the expansion of the market for these fuels. Several proposed pathways try to account for NOx formation during the combustion process. Among them, the Fenimore mechanism explains that fuel radicals formed during the combustion process react with nitrogen from the air to form NOx. It could be proposed that if these radical reactions could be terminated, the NOx formation rate for biodiesel combustion would decrease. An experimental study was conducted on a four-cylinder diesel engine to evaluate the performance and emission characteristics of Jatropha biodiesel blends (JB5, JB10, JB15 and JB20) with and without the addition of N,N′-diphenyl-1,4-phenylenediamine (DPPD) antioxidant. For each tested fuel, the engine performance and emissions were measured at engine speeds 1000–4000rpm at an interval of 500rpm under the full throttle condition. The results showed that this antioxidant additive could reduce NOx emissions significantly with a slight penalty in terms of engine power and Brake Specific Fuel Consumption (BSFC) as well as CO and HC emissions. However, when compared to diesel combustion, the emissions of HC and CO with the addition of the DPPD additive were found to be nearly the same or lower. By the addition of 0.15% (m) DPPD additive in JB5, JB10, JB15 and JB20, the reduction in NOx emissions were 8.03%, 3.503%, 13.65% and 16.54% respectively, compared to biodiesel blends without the additive under the full throttle condition. Moreover, the addition of DPPD additive to all biodiesel blend samples reduced the exhaust gas temperature.

Experimental study on performance and exhaust emissions of a diesel engine fuelled with Ceiba pentandra biodiesel blends

Nowadays, production of biodiesel from non-edible feedstock is gaining more attention than edible oil to replace diesel fuel. Thus, Ceiba pentandra is chosen as a potential biodiesel feedstock for the present investigations based on the availability in Indonesia and Malaysia. C. pentandra methyl ester was prepared by two-step acid esterification (H2SO4) and base transesterification (NaOH) process. The purpose of this study is to examine the engine performance and emission characteristic of C. pentandra biodiesel diesel blends in internal combustion. Besides, the detailed properties of C. pentandra biodiesel, biodiesel diesel blends and diesel were measured and evaluated. After that, the biodiesel diesel blends (10%, 20%, 30% and 50%) were used to conduct engine performance and exhaust emission characteristic at different engine speeds. The experimental results showed that CPB10 blend give the best results on engine performance such as engine torque and power at 1900rpm with full throttle condition. Besides, the brake specific fuel consumption at maximum torque (161g/kWh) for CPB10 is higher about 22.98% relative to diesel fuel (198g/kWh). This is shown that the lower biodiesel diesel blends ratio will increase the performance and reduce the fuel consumption. Moreover, the exhaust emissions showed that CO, HC and smoke opacity were reduced for all biodiesel diesel blends. However, NOx and CO2 were increased compared to petrol diesel. Overall, the results proved that C. pentandra biodiesel is a suitable alternative and substitute fuel to diesel.

Performance, combustion and emission characteristics of a spark-ignition engine with simultaneous injection of n-butanol and gasoline in comparison to blended butanol and gasoline

SUMMARY Simultaneous injection of n-butanol and gasoline through a new system of two injectors directing the sprays towards the back of the intake valve in a spark-ignition engine was tried in lieu of injecting a blend of these fuels through a single injector. This system avoids the problem of phase separation, which is generally faced during the use of alcohol-gasoline blends. Experiments were conducted on a spark-ignition engine with this dual injection system using a fuel ratio of 1:1 (B50S) on the mass basis. High-speed photographs indicated that the sprays from the injectors did not interfere till they reached the intake valve. Comparisons were made with pre-blended butanol-gasoline (B50) and neat (100%) gasoline at the best spark timing. All injection and spark parameters were controlled using a real time engine controller. Neat n-butanol (B100) was superior only near full throttle with improved efficiency of the engine of about 1.2% (absolute). Heat release rates were observed to be higher and more advanced with B100 at wide open throttle. However, a reverse of this trend was observed at the throttle position of 15%. NO emission was also lower by 30% with B100 at wide open throttle as compared with gasoline. However, a small increase in carbon monoxide (CO) levels was observed because of lower post combustion temperatures as compared with gasoline and B50S. Simultaneous injection reduced hydrocarbon (HC) emissions by 13% to 50% as compared with B50 (blended fuel). HC emissions with gasoline and B50S were similar. Nitric oxide (NO) emission was lower with B50S as compared with gasoline; however it was higher than B50 because of better combustion. On the whole, the developed dual injection system was superior to the conventional method of blending in terms of performance, emissions and ability to change the fuel ratio as needed. B50S is suitable at all throttle positions, whereas B100 shows benefits at full throttle conditions. Copyright © 2013 John Wiley & Sons, Ltd.

Hand-Arm Vibration of Unskilled Oil Palm Motorised Cutter Operator

The portable petrol driven oil palm motorised cutter or CANTAS has been identified as a type of machine that generates hand-arm vibration. These vibrations can cause complex vascular, neurological and musculoskeletal disorder known as hand-arm vibration syndrome (HAVS) when over exposure of daily usage. The objective of this study is to investigate the vibration level at different angles during the operational of the CANTAS including idle and full throttle conditions. The CANTAS vibration experiments were carried out at a farm in Parit Raja, Batu Pahat, Johor. A student participated as the unskilled worker and was assisted by two technical staffs to conduct the vibration measurements. The measurement was taken during the operations of cutting first fronds, second fronds and a fruit bunch during idle and full throttle conditions and by varying the inclination angle. The inclinations of cutting angle were varied from 45º, 60º and 75º. The hand-arm vibration value, ahv achieved 10.93 ±1.2 m/s2 and 7.94 ± 1.0 m/s2 for unskilled user during operation of two bunches and one pruning frond for all angles at point 1 and point 2 handle respectively. Mean vibration values at both point of handles resulted in vibration values of 10.12±3.8m/s2 at 450, 9.15±3.0m/s2 at 600 and 9.03±1.8m/s2 at 750. Increasing the angle overall results in decreasing the level of vibration at both handle points.

Hand-Arm Vibration Analysis of Palm Oil Fruit Harvester Machine

The objective of this study is to determine the vibration value of Palm Oil Harvester Machine or CANTAS motorized cutter profile. The CANTAS machines have been divided into twelve nodes and hand arm vibration measurements are taken for idle and full throttle operation. Three cutting heads provided by MPOB have been measured for comparison purposes. The hand-arm vibration values for Type A Cutting head achieves (3.89±1.10) m/s2 for idle condition and (10.71±2.88) m/s2 for full throttle condition. Meanwhile Type B Cutting Head achieves (3.63±0.87) m/s2 for idle condition and (11.22±1.74) m/s2 for full throttle condition. Type C of Cutting Head yields (3.51±0.82) m/s2 for idle condition and (15.54±3.81) m/s2 for full throttle condition along the structure. The results also shows which points depicted highest vibration level during idle (no operation, ideally from tree to tree) and full throttle (overuse operation). These values present the maximum and minimum vibration levels that will be received by the user in daily usage of the machine. design in reducing vibration to the hand-arm of the user.

Mixture Preparation in a Four-Stroke Compression Ignition Engine – A CFD Approach

A CFD simulation is carried out to predict the effects of piston crown on the fluid flow field, inside the combustion chamber, cylinder of four strokes CI engine. The complete analysis is concentrated on the study of effects of the piston shape. On the fluid flow characteristics, fluid flow dynamics exhibits an important role on charge preparation to attain the better combustion performance and efficiency in the viscosity of swirl and tumble flows as turbulence. The turbulence parameters like swirl and tumble represents the fluid flow behavior occurs inside the combustion chamber, which influence the air streams to the cylinder during intake stroke and reasonably enhances the mixing of air and fuel to have a better mixing during compression stroke. The numerical calculations are preferred in a single cylinder four stroke diesel engine running at full throttle condition by using the CFD mode. Different Bowls are considered with an engine speed of 2200 rpm, for this analysis, to be compared to evaluate the swirl and tumble flows produced during intake and compression stroke. The results obtained from the numerical analysis can be used to predict uniformity in the structure of a charge for a efficient performance and combustion in a compression ignition engine.

Power boosting of a modified natural gas engine

This paper presents the experimental results on brake power enhancement of a modified natural gas engine. Conventional natural gas engine produces 15 to 20% less brake power than that of gasoline fired engine. This lacking in compressed natural gas (CNG) engine needs to be recovered through modifications and optimization of fuel injection system to provide complete gas combustion in the engine cylinder. A multi-cylinder gasoline engine was modified to bi-fuel engine for operating in several test conditions, such as constant full and half throttle condition. Variation in power production with corresponding fuel flow rate and emission gases (such as carbon monoxides, CO; unburnt hydrocarbon, HC and nitrogen oxides, NOx) were studied by using two fuels (gasoline and CNG). Engine tune up information like variation in air fuel ratio (AFR) for lean burn operation can be known from those tests. Performance of engine was studied with both the fuels at fixed load and the corresponding fuel flow rate and emissions were measured for evaluation and optimization. The engine produced 10% higher brake power with CNG fuel as compared to that produced with gasoline fuel at full load, but at partial load gasoline fuel produced more brake power than CNG. Emission results revealed that CNG fuelled engine emits less CO and HC, showing more complete combustion than gasoline fuel. On the contrary, higher combustion temperature of CNG fuel produced more NOx than gasoline. The results of these investigations can be used to develop a new compressed natural gas (CNG), direct injection (DI) and higher efficiency engine in the near future to build an environment friendly fuel economic clean burning automotive vehicle with less emission and similar power rating like gasoline engine. Key words: Brake power, compressed natural gas-direct injection (CNG-DI), bi-fuel engine, fuel consumption, emission.

Finite-element analysis of quasistatic fracture in CV joints under full-turn and full-throttle conditions

Quasistatic fractures at high joint angles constitute a chronic quality problem in CV joints. This type of fracture occurs when a driver unintentionally depresses the brake and accelerator simultaneously under a full-turn retreat condition. In general, the cage in a ball joint can be broken only at these high joint angles. Here we present a flexible quasistatic simulation model developed to simulate fracture in a CV joint. The cause and process of the quasistatic fracture were analyzed using simulations and physical tests. Static fracture simulations and tests at high joint angles showed that, initially, only one of the six cage posts was damaged. In a simulation of one revolution at constant torque, we found that an imbalance in ball loads generated an excessive cage load. Moreover, if this high cage load was applied when the cage protruded outward, the cage post was subjected to severe shear loading. The cage post was damaged in this specific rotational range. Quasistatic fracture simulations and tests at high joint angles showed that all six cage posts were damaged sequentially. Because entire cage posts were damaged, the quasistatic fracture torque was approximately half of the static torque. The plastic strain in each cage post displayed one step-like jump per revolution in the quasistatic simulations. The ball indentation created by a high ball load was interrupted by the cage-window edges as the ball joint rotated. This hindrance by ball indentation triggered the final breakage of the cage, although it was not the major cause of cage fractures.

Design of Supercavitating Propellers for a Racing Boat

This paper describes the successful application of a theoretical supercavitating propeller design method to racing boat propellers. Two propellers were designed, manufactured and tested on a newly developed full-scale boat.The first one, the SC-2 propeller, was designed at an advance ratio of 1.371 and a cavitation number of 0.3, and tested at the Kiryu racing site together with two target propellers, the SC-1 propeller which was previously designed by a Bp-chart method, and a commercial racing boat propeller, the “Record Propeller”. No remarkable difference in the measured speeds of the racing boat equipped with each propeller was observed at full throttle condition, while the performance of the SC-2 propeller was superior to that of the SC-1 propeller at the prescribed design conditions in tests in two cavitation tunnels.The second propeller, the SC-3 propeller, was designed by changing the propeller diameter from 165 mm to 175 mm to make the diameter more optimum at an advance ratio of 1.197. The blades of this propeller were designed to be as thin and narrow as possible to get the optimum lift-drag ratio at each radial position within the limitation of having the same strength requirement as that for the SC-1 propeller. At the propeller root, aerofoil blade sections were applied from the view points of strength and efficiency.The second propeller was also tested at the racing site with the SC-1, the SC-2 and another famous commercial propeller, the “Rolla Propeller”. The racing boat with the SC-3 propeller ran at the highest speed of about 97 km/h in the full-scale test. At the racetrack, a running test around two turning buoys 300 m apart gave the following results ; the racing boat with the SC-3 propeller completed a lap within 33.8 seconds which was 1.4 seconds faster than that with the “Rolla Propeller”. The test in cavitation tunnels endorsed the higher performance of the SC-3 propeller than those of other propellers.