Throttle Conditions Research Articles

Simulation of Broadband Noise Sources of an Axial Fan under Rotating Stall Conditions

Study on the influence of rotating stall on the aerodynamic noise of axial fan has important value to warn of the occurrence of stall through monitoring the noise variations. The present work is to analyze the aerodynamic noise before and after the phenomenon of rotating stall by solving Navier-Stokes equations, coupled with the throttle condition and the broadband noise sources model. The impeller exit rotational Mach number and rotational Reynolds number are separately 0.407 and 8.332 × 106. The results show that the aerodynamic noise source of the fan is mainly the rotation noise under the design condition. The vortex noise accounts for the major part of fan noise after the occurrence of stall, and the maximum acoustic power level of the fan appears in the rotor domains. In the evolution process from the stall inception to the stall cell, the high noise regions of the rotor develop along the radial, circumferential, and axial directions, and the area occupied by high noise regions increases from 33% to 46% impeller channels area. On rotating stall condition, the high noise regions occupying about 46% impeller channels area propagate with the stall cell along the circumferential direction at a half of rotor speed.

A Power Generation Study of a Power Pack Based on Operating Parameters of the Linear Engine Fuelled with Propane

In this paper, we present our experimental research on a power pack based on operating conditions of the linear engine and the linear generator structure for generating electric power. The power pack used in the study consisted of a two-stroke free-piston linear engine, linear generators, and air compressors. Each parameter of input caloric value, equivalence ratio, spark timing delay, electrical resistance, and air gap length were settled for identifying the electrical power generation of the linear engine. The linear engine was fueled with propane, and in the course of all its operations, intake air was inputted under the wide open throttle condition. The air and fuel mass flow rate were varied by a mass flow controller and premixed by a pre-mixing device. The premixed gas was then directly supplied into each combustion cylinder. The experiments confirmed that power generation was induced differently for each respective operating condition. The maximum generating power was found with the value of 111.3W, where the operating conditions were as follows: 1.0 of equivalence ratio, 1.5ms of spark timing delay, 30Ω of electric resistance, and 1.0mm of air gap length.</abstract>

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.

EGR Effect On Performance of a Spark Ignition Engine Fueled with Blend of Methanol-Gasoline

This paper examines the results of performance of a single cylinder spark- ignition engine fuelled with 20% methanol +80% gasoline (M20), compared to gasoline. The experiments were conducted at stoichiometric air–fuel ratio at wide open throttle and variable speed conditions, over the range of 1000 to 2600 rpm. The tests were conducted at higher useful compression ratio using optimum spark timings and adding recirculated exhaust gas with 20% to suction manifold.&#x0D; The test results show that the higher compression ratio for the tested gasoline was 7:1, 9.5:1 for M20 and 9:1 for M20 with added EGR. M20 at higher useful compression ratio (HUCR) and optimum spark timing (OST) characteristics are significantly different from gasoline. Within the tested speed range, M20 consistently produces higher brake thermal efficiency by about 6%. Also it resulted in approximately 3.06% lower brake specific fuel consumption compared with gasoline. Adding EGR to M20 caused reduction in HUCR and advancing the OST. This addition increased brake specific fuel consumption (BSFC), reduced brake thermal energy, volumetric efficiency and exhaust gas temperatures.

Solar cogeneration power-desalting plant with assisted fuel

Solar power plants (SPP) using parabolic trough solar collectors operating Rankine steam cycle are well proven and most widely used worldwide. These plants have low-power cycle efficiency (30%) due to low throttling conditions of 350–375°C and 100 bar. Conventional steam power plants have high throttling conditions (535–560°C and 140–160 bar) and high efficiency (38–40%). Qatar is endowed with abundance of natural gas (NG) resources and production. Qatar’s power plants use natural gas-operated gas turbines. However, resources are finite and domestic consumption is rising because of rapid economic and population growth. As in many countries, SPPs are considered to take share in electric power and desalted seawater productions. This elongates the life of the NG resources, and keeps the income return from its exporting. This also limits the emission of greenhouse gases and air polluting gases due to NG combustion, which badly affects the environment. While NG is used in SPP to compensate solar energy intermittent nature and keeps operation during non-sunshine hours, the main purpose of using NG here is to raise the SPP throttling temperature, and thus increasing steam cycle efficiency, even during full sun shine. It also lowers using expensive land where the SPP is planned. This paper studies the feasibility of utilizing NG to superheat the steam leaving the SPP solar collector field, and to heat the feedwater to the collector. This drastically increases both power output and efficiency. Modifications of SPP power cycle to become cogeneration power desalting plants are presented.

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.

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.

Effect of Throttle Conditions on Fluid Dynamic Instabilities in Axial Compression Systems

An analysis of the effect of throttling on surge and rotating stall has been done to develop an insight on the possible behaviour of instabilities in a compression system subsequent to an initial disturbance. The ability to predict the nature of instabilities are highly important from the compressor design point of view since their consequences could result in widely varying difficulties with the fluid dynamic performance of the systems. The present paper discusses, in an approximate manner, the effect of throttle position in a compressor performance curve which is shown to create widely varying behaviour on fluid dynamic instabilities once the stall line is crossed. The physical reason for the behaviour is explained and the well-established Moore–Greitzer compression system model have been used for the present study. The results shown in this paper clearly elucidates the dominating effect of the operating parameter, the throttle, on the development of flow instabilities like rotating stall and surge. The trends of their behaviour reported in this paper are found to have a good agreement with the experimental results. As these results inform about the nature of instabilities that one could expect as the stall line is crossed, appropriate preventive measures could be adopted to avoid/control such instabilities.

Doha solar cogeneration power desalting pilot plant: Preliminary design

High solar intensities in Qatar can be utilized to generate some of its own electric power (EP) needs. Thermal concentrated solar power (CSP) can also be used to generate EP. In thermal CSP, direct solar irradiance produces heat that generates steam to generate EP. This mature commercial technology is ready for implementation. Qatar National Food Security Programme proposes to implement the usage of solar energy to produce desalted seawater (DW). To support such efforts, Qatar Environment and Energy Research Institute is planning on building a solar pilot plant to produce EP and DW, i.e. a solar cogeneration power desalting plant (CPDP) in Doha. The objectives of this would be to determine the viability of using solar energy to produce both EP and DW and to assess the possibilities of a natural gas-assisted steam cycle to improve the efficiency of the solar CPDP by raising the throttling conditions to reduce the capital cost and the produced EP final cost. The pilot plant will also help in scaling up to b...

Effects of Angles of Attack and Throttling Conditions on Supersonic Inlet Buzz

A series of numerical simulations are carried out to analyze a supersonic inlet buzz, which is an unsteady pressure oscillation phenomenon around a supersonic inlet. A simple but efficient geometry, experimentally adopted by Nagashima, is chosen for the analysis of unsteady flow physics. Among the two sets of simulations considered in this study, the effects of various throttling conditions are firstly examined. It is seen that the major physical characteristic of the inlet buzz can be obtained by inviscid computations only and the computed flow patterns inside and around the inlet are qualitatively consistent with the experimental observations. The dominant frequency of the inlet buzz increases as throttle area decreases, and the computed frequency is approximately 60Hz or 15% lower than the experimental data, but interestingly, this gap is constant for all the test cases and shock structures are similar. Secondly, inviscid calculations are performed to examine the effect regarding angle of attack. It is found that patterns of pressure oscillation histories and distortion due to asymmetric (or three-dimensional) shock structures are substantially affected by angle of attack. The dominant frequency of the inlet buzz, however, does not change noticeably even in regards to a wide range of angle of attacks.

Impact of Manufacturing Variability on Multistage High-Pressure Compressor Performance

The present paper introduces a novel approach for considering manufacturing variability in the numerical simulation of a multistage high-pressure compressor (HPC). The manufacturing process is investigated by analyzing three of a total of ten rotor rows. Therefore, 150 blades of each of the three rows were 3D scanned to obtain surface meshes of real blades. The deviation of a scanned blade to the design intent is quantified by a vector of 14 geometric parameters. Interpolating the statistical properties of these parameters provides the manufacturing scatter for all ten rotor rows expressed by 140 probability density functions. The probabilistic simulation utilizes the parametric scatter information for generating 200 virtual compressors. The CFD analysis provides the performance of these compressors by calculating speed lines. Postprocessing methods are applied to statistically analyze the obtained results. It was found that the global performance parameters show a significantly wider scatter range for higher back pressure levels. The correlation coefficient and the coefficient of importance are utilized to identify the sensitivity of the results to the geometric parameters. It turned out that the sensitivities strongly shift for different operating points. While the leading edge geometry of all rotor rows dominantly influences the overall performance at maximum efficiency, the camber line parameters of the front stages become more important for higher back pressure levels. The analysis of the individual stage performance confirms the determining importance of the front stages—especially for highly throttled operating conditions. This leads to conclusions regarding the robustness of the overall HPC, which is principally determined by the efficiency and pressure rise of the front stages.

Naturally aspirated and boosted controlled auto-ignition combustion with positive valve overlap in a four-stroke gasoline engine

Extensive engine experiments were carried out on controlled auto-ignition combustion, also known as homogeneous charge compression ignition, in a four-stroke gasoline engine, by internally recycling burned gases through positive valve overlap, variable compression ratio, intake temperature control and boosting. The operational range of controlled auto-ignition combustion was determined for a range of compression ratios and intake air temperatures at wide-open throttle conditions. This was followed by further engine experiments with boosted intake and external exhaust gas recirculation in order to evaluate their effect on the operational range of controlled auto-ignition combustion and the engine’s performance and emissions. It has been found that the controlled auto-ignition operational region could be extended to the higher load region by boosting and running with leaner mixtures, whilst the use of external exhaust gas recirculation allowed the engine to operate controlled auto-ignition combustion optimized in the region between naturally aspirated and lean boosted controlled auto-ignition operational regions. The highest fuel conversion efficiency was obtained when the exhaust heat could be utilized to supply the intake air heating.

Internal Flow and Noise Investigations About the Cross-Flow Fan With Different Blade Angles

The experimental and numerical studies have been carried out to investigate the flow and the noise characteristics of the three impellers with different blade angles in a cross-flow fan (CFF). First, the aerodynamic performances of the fan with these impellers are obtained experimentally, and the averaged flow patterns inside the impellers are measured by the three-hole probe. Second, the far-field noise generated by CFF with different impellers has been measured in a semianechoic chamber under different throttling conditions. Third, the two-dimensional unsteady CFD simulations have been performed by commercial software. The internal flow patterns influenced by the different blade angles have been summarized through the computational results. The accuracy of the calculations is validated by the corresponding experimental ones. The detail analysis has been carried out on the unsteady vortex flow properties of the three impellers, which is considered to be the main factor that influences the aerodynamic and aeroacoustic performance of the CFF. Finally, the relative far field noise generated by different impellers are evaluated by an empirical formula based on the assumption that the total sound pressure levels are proportional to the sixth power law of the relative velocity on the outer and inner circumferences of the impeller. The circumferential distributions of relative velocity are provided from the numerical solutions. The varying trends of predicted results agree well with the actual relative noise of the CFF with three different impellers.

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 output characteristics of hydrogen-natural gas blend fuel engine at different compression ratios

Potential and knocking characteristics of a hydrogen-natural gas blend (HCNG) engine with a high compression ratio were examined from a commercial viewpoint since lean combustion with HCNG under a wide-open throttle (WOT) condition requires a high-charging-capacity turbocharger. Supercharging of intake air to extend the lean limit was investigated for a turbocharged, heavy-duty natural gas-fueled engine. Effects of compression ratio changes on fuel economy were assessed in terms of thermal efficiency and torque characteristics. Extension of the lean limit to an excess air ratio of 1.8 for an HCNG engine under WOT conditions is realizable using a supplementary supercharging system. Thermal efficiency improvement at high compression ratios is reduced under relatively rich mixture conditions because spark timing is retarded to avoid knocking. The excess air ratio corresponding to maximum thermal efficiency decreases to 1.6 for an HCNG engine due to the decrease in exhaust gas energy for intake-air charging.

Experimental study of hydrous ethanol gasoline blend (E10) in a four stroke port fuel-injected spark ignition engine

SUMMARY Performance, emissions and combustion characteristics of a port-injected engine fuelled with hydrous ethanol gasoline blend (E10 - 10% of hydrous ethanol by volume in gasoline) were compared with gasoline operation. Hydrous ethanol blend produced higher power output with lean mixtures at part throttle condition. Higher flame velocity and wider flammability limits of the blend resulted in lower cycle-by-cycle variations in indicated mean effective pressure as compared to gasoline. Hydro carbon emission was also lower due to the oxygen available in the fuel (E10), which enhanced the combustion rate. Higher latent heat of evaporation of the ethanol blend and water present in it resulted in lower in-cylinder temperature, which in turn led to lesser NOx emissions. Thermal efficiency with the blend was higher in the leaner operating conditions than gasoline. Not much difference in performance, emission and combustion characteristics between neat gasoline and E10 were observed at full throttle operation. On the whole, hydrous ethanol blends can be used as a fuel with good performance and low emissions at part load condition. Copyright © 2012 John Wiley & Sons, Ltd.

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.

Artificial Neural Network and stepwise multiple range regression methods for prediction of tractor fuel consumption

Predicting tractor fuel consumption can lead to selection of the best conservation practices for farm equipments. In present study for estimating tractor fuel consumption was used from the Nebraska Tractor Test Lab (NTTL) data. Fuel consumption was assumed to be a function of engine speed, throttle and load conditions, chassis type, total tested weight, drawbar and PTO power. Back propagation Artificial Neural Network (ANN) models with six training algorithms were adopted for predicting fuel consumption. The highest performance was obtained for the network with two hidden layers each having 10 neurons which employed Levenberg–Marquardt training algorithm. Results indicated that the ANN and stepwise regression models represented similar determination coefficient ( R 2 = 0.986 and R 2 = 0.973, respectively) while the ANN provided relatively better prediction accuracy ( R 2 = 0.938) compared to stepwise regression ( R 2 = 0.910). One of the advantages of ANN model was integration of load and throttle condition in the form of one model.