Engine Rpm Research Articles

Characterization of Submicron Exhaust Particles from Engines Operating Without Load on Diesel and JP-8 Fuels

Diluted exhaust from a selection of Air Force ground support vehicles was subjected to gravimetric, carbon, and size distribution analyses in September 1999. The vehicles operated on diesel and JP-8 fuels. In most cases, the engines involved were similar to civilian counterparts. The tests involved low and high idle settings but no external loads were imposed. Particle size distribution data, obtained over the 10 to 352 nanometer diameter range using an SMPS instrument, showed that the relative number count of accumulation mode particles increased with respect to nucleation mode particles as the engine rpm increased. The SMPS distributions often explained the main variations in the integrated PM 2.5 gravimetric mass data. Particulate mass derived from the SMPS data and from cascade impactor measurements were well correlated (regression slope 1.02). Empirically determined elemental carbon (EC) and organic carbon (OC) were the main constituents of the PM 2.5 gravimetric mass (regression slope 0.89)....

New active muffler system utilizing destructive interference by difference of transmission paths

A new active muffler system has been developed and its superior performance on both noise reduction and engine torque increase is demonstrated with experiment. Main characteristic of the proposed muffler system is the use of destructive interference by transmission path difference of divided exhaust pipes to reduce major exhaust noise components thereby overcoming problems of other active exhaust noise control methods. The exhaust pipe is divided into two sections and joined again downstream. One divided pipe has a sliding mechanism to vary its length, which is controlled to make half wavelength transmission path difference for the major engine rpm frequency. In this system one divided pipe is used to control major rpm frequency and its Harmonics and another pipe is used to control noise component double the frequency of rpm. An after-market tuning muffler, which has very simple internal structure and minimal back pressure, is also installed to remove remaining wideband noise. To make the system to be small enough to be practical, conventional muffler is also installed and used in low rpm range and active muffler is only employed in high rpm range. Noise reduction of the proposed system is comparable to conventional passive muffler. The engine dynamo test has proved the proposed system can recover almost all the torque lost by conventional muffler.

농용 트랙터용 작업기 승.하강 제어시스템에 관한 연구

Rotary and plow implements are mainly utilized for the tillage operation in Korea, and a implement control system for agricultural tractors was designed and fabricated to improve the working accuracy and efficiency. The control system was composed of three units: 1) sensors fur detection of angle of liftarm, draft force, engine rpm, tillage depth and so on, 2) a controller, and 3) hydraulic circuits, which included solenoid valves and so on, for operation of three point linkage and implements. The control system can control the speed(high and low speed) of implements by adjusting input flow rates of the hydraulic cylinder which was controled by two speed valve, which was composed of a solenoid valve and a orifice. Indoor experiments were conducted to evaluate response characteristics of the designed implement control system under experimental conditions of various engine nm, two kinds of input flow rates of the cylinder and some input frequency. The results of experiments showed the response characteristics sufficient to use as the implement control system fur agricultural tractors.

Characteristics of small boat acoustic signatures

Small boats are often a dominant noise source in harbors, coastal regions, and lakes. However, detailed information about acoustic characteristics is not generally available. To remedy this deficiency, measurements of underwater acoustic signatures from various small boats have been conducted under controlled conditions. Boats used in the measurements were powered by a variety of gasoline and diesel motors in outboard, inboard–outboard, and inboard drive configurations. Measurements were made using a bottom mounted hydrophone in about 100 feet of water. In many instances, the boats were instrumented with a system that recorded the GPS position and engine RPM permitting accurate determinations of platform operating parameters. Measured small boat signatures contain both narrowband and broadband acoustic components. Narrowband components are generally associated with sources from the engine or drive. Narrowband levels in the observed spectra were found to exhibit significant variations and are believed to originate from fluctuations in the load on the engine and drive. Broadband energy was observed to be a dominant noise source at frequencies above several hundred Hertz and is a characteristic feature in all small boat signatures. Examples of small boat signatures will be presented and representative acoustic characteristics of this type of watercraft will be discussed.

전달경로의 차이를 이용한 새로운 차량용 능동 머플러의 개발

A new active muffler system has been developed and its superior performance on both noise reduction and engine torque increase is demonstrated with experiment. Main characteristic of the proposed muffler system is the use of destructive interference by transmission path difference of divided exhaust pipes to reduce major exhaust noise components thereby overcoming problems of other active exhaust noise control methods. The exhaust pipe is divided into two sections and joined again downstream. One divided pipe has a sliding mechanism to vary its length, which is controlled to make half wavelength transmission path difference for the major engine rpm frequency. In this system one divided pipe is used to control major rpm frequency and its Harmonics and another pipe is used to control noise component double the frequency of rpm. An after-market tuning muffler, which has very simple internal structure and minimal back pressure, is also installed to remove remaining wideband noise. To make the system to be small enough to be practical, conventional muffler is also installed and used in low rpm range and active muffler is only employed in high rpm range. Noise reduction of the proposed system is comparable to conventional passive muffler. The engine dynamo test has proved the proposed system can recover almost all the torque lost by conventional muffler.

Formaldehyde Formation in Large Bore Engines Part 2: Factors Affecting Measured CH2O

Current research shows that the only hazardous air pollutant of significance emitted from large bore natural gas engines is formaldehyde CH2O. A literature review on formaldehyde formation is presented focusing on the interpretation of published test data and its applicability to large bore natural gas engines. The relationship of formaldehyde emissions to that of other pollutants is described. Formaldehyde is seen to have a strong correlation to total hydrocarbon (THC) level in the exhaust. It is observed that the ratio of formaldehyde to THC concentration is roughly 1.0–2.5 percent for a very wide range of large bore engines and operating conditions. The impact of engine operating parameters, load, rpm, spark timing, and equivalence ratio, on formaldehyde emissions is also evaluated. [S0742-4795(00)01004-8]

Automação do processo de avaliação de desempenho de tratores e implementos em campo

Em muitas regiões do Brasil, tratores e implementos agrícolas têm sido usados para dar suporte aos diferentes sistemas de produção, sem uma adequação própria às condições de solo e clima. Para auxiliar os fabricantes e agricultores na solução de problemas em máquinas e implementos agrícolas, há necessidade de verificar o desempenho desses equipamentos e estabelecer condições de testes semelhantes àquelas em que estiveram sendo usados. Este trabalho teve como objetivo avaliar o desempenho de um conjunto tratorimplemento agrícola, no campo, utilizando um sistema eletrônico de medições. A potência demandada pelos equipamentos foi calculada indiretamente, com os dados de rotação do motor e consumo de combustível, nas curvas de calibração do trator. O uso de instrumentação eletrônica permitiu que se tivesse uma grande capacidade de trabalho, em razão da facilidade de programação e operação da cadeia de medições. Os resultados de campo obtidos para esforço de tração líquida indicaram tendência de comportamento similar à dos calculados por meio de fórmulas, com uma correlação de 0,996. A metodologia utilizada nos testes de desempenho operacional do conjunto trator-implemento no campo indicou ser uma ferramenta de bastante utilidade, tanto para os usuários dos equipamentos, quanto para os fabricantes.

Fixed-Pitch Propeller/Piston Aircraft Operations at Partial Throttle

The linearized propeller polar or bootstrap approach to e xed-pitch propeller aircraft performance is extended to include partial-throttle operations. Power setting parameter P is dee ned as the ratio of actual engine torque to maximum possible (full-throttle ) torque at the given atmospheric density. To compute quasisteady partial-throttle performance, two additional data items, beyond the nine items of the ordinary bootstrap data plate, are required: 1) brake specie c fuel consumption rate as a function of engine power and 2 ) level cruise speeds with associated engine speeds (from a e ight test at any one altitude and weight ). The latter results in a propeller chart giving advance ratio J as a function of CP/J 2 , the independent variable in the propeller polar. With that information, level cruise performance tables (similar to GAMA format, but extended with thrust and propulsive efe ciency ) can be calculated. Installed propeller charts can be constructed and expressions for partial-throttle absolute ceilings derived. Given the airplane’ s airspeed and desired e ight path, e.g., a standard rate turn descending 300 ft/min at 90 KCAS, engine rpm required for that maneuver can then readily be calculated. This partial-throttle facility rounds out the bootstrap approach, allowing full prediction of quasisteady performance of e xed-pitch propeller airplanes.

Estimation of Tire-Road Friction Using Observer Based Identifiers

This paper presents methods for identifying the tire-road friction coefficient. The proposed methods are: an observer-based least square method and an observer/filtered-regressor-based method. These methods were designed assuming that some of the states are not available since physical parameter identification methods developed assuming that the system states are available are not attractive from a practical point of view. The observer is used to estimate signals which are difficult or expensive to measure. Using the estimated states of the system and the filtered-regressor, the parameter estimates are obtained. The proposed methods are evaluated on an eight state nonlinear vehicle/transmission simulation model with a Bakker-Pacejka's formula tire model. Vehicle tests have been performed on dry and wet roads to verify the performance of the methods. It has been shown through simulations and vehicle tests how the RPM sensors can be used with observer based identification methods to estimate the tire-road friction from measurements of engine rpm, transmission output speed and wheel speed. The proposed methods will be useful in the implementation and adaptation of vehicle collision warning/avoidance algorithm since the tire-road friction can be estimated only using the RPM sensors which are currently being used in production vehicles.

Sound quality evaluation of vehicle interior power train noise

In this paper, the sound quality of interior noise of three 1500-cc passenger cars driving at constant speed is evaluated. Paired comparison for three different cars and engine rpm was applied for subjective assessment with respect to important factors, i.e., booming, roughness, sharpness, powerfulness, and loudness. Based on the results, loudness is the most important factor on the perceived annoyance. Finally, an objective measure to evaluate: Each of five factors was conducted and each of these measures had good correlation and subjective evaluation. [See NOISE-CON Proceedings for full paper.]

Evaluation of a 6.71 kW power tiller for draft and drawbar power on tar roads

A 6.71 kW power tiller was evaluated for draft and drawbar power on tar roads. The effect of mounting 40 kg of wheel ballast was also studied. Polynomial regression analysis was used to establish the relationship between draft and wheel slip, drawbar power and wheel slip, drawbar power and fuel consumption, and drawbar power and specific fuel consumption. The results of the study showed draft values of 2107, 2110 and 2110 N in second low, third low and first high gears at an engine speed of 150o rpm with a 15% wheel slip. The respective draft values at engine speed of 2000 rpm with a 15% wheel slip were 2172, 2189 and 2212 N. With the mounting of 40kg wheel ballast there was an increase in draft of 217, 207 and 291 N at 1500 rpm, and 328, 306 and 344 N at 2000 rpm of the engine with a 15% wheel slip in second low, third low and first high gears, respectively. The increase in drawbar power with 40 kg ballast was 10.88%, 7.83% and 20.13% at 1500 rpm and 18.89%, 16.56% and 14.88% at 2000 rpm of engine over the drawbar power available with zero ballast. The fuel consumption with the use of wheel ballast was slightly more than the fuel consumption without any ballast.

Zero-thrust glide testing for drag and propulsive efficiency of propeller aircraft

The authors have developed a new method, zero-thrust glide testing, that provides the first really practical, accurate, and inexpensive method for measuring the drag of propeller aircraft in gliding flight. Zero-thrust conditions were sensed on a classic Luscombe 8£ by monitoring the fore and aft clearance motion of the engine crankshaft as the engine rpm or power was changed. With zero engine thrust conditions, gliding flight measurements were made to find the drag polar and propeller airfoil zero-lift angles. The glide polar and level flight measurements have been used to find the propulsive efficiency. The airfoil zero-lift angles were used to accurately calculate the propeller thrust, and therefore, the drag in powered level flight. Drag in level flight cruise is approximately 30% larger than in glide, resulting in a propulsive efficiency equal to 0.62. Propeller efficiency has been calculated using standard methods corrected for the interference between the propeller and the airframe flowfields. The interference changed the propeller thrust, created an inviscid buoyancy drag on the fuselage, and generated viscous-related drag forces. The viscous forces and engine cooling duct losses are the cause for the poor propulsive efficiency and are believed to be typical of many propeller-driven aircraft.

Synchronous active noise cancellation with LPC noise synthesizer

A new active noise cancellation scheme has been developed for the purpose of engine noise cancellation. The major difference between the new approach and the conventional two‐microphone adaptive noise cancellation methods is that the new approach does not require the reference signal. Therefore, the problem of acoustical feedback from the canceling speaker to the reference channel is eliminated. In this new scheme, a linear predictive coding (LPC) technique is employed to synthesize an “engine noise,” which is used as a reference signal, and this synthesized noise is processed by an LMS adaptive filter. Simulation results using a set of digitized engine noise data show that the adaptive filter has a faster convergence rate and more than 10‐dB mean‐squared error improvement by using an LPC noise synthesizer in comparison with using an impulse train as input only. In the case that engine speed is varying or the engine rpm is not available, a multipulse excitation synthesizer has been used to generate the synthesized engine noise. The multipulse excitation method has also provided an improvement of 10 dB in mean‐squared error.

Flame Front Propagation in Nonsteady Hydrodynamic Fields

Abstract We show asymptotically and numerically that a constant-density flame will exhibit different geometrical shapes which depend on the flow time-scales. In particular, a frozen flow may yield a flame surface composed of bulges connected by cusps, whereas a pulsating flow may dampen the flame motion to the extent that only a flat, laminar flame surface will be possible. The cusp nature disappears when the eddy frequency becomes comparable to uLk, where uL is the laminar flame speed and k is a characteristic wave number of the flow. Flame shapes obtained with a sheet of laser light within a spark-ignited engine show a cusp nature only at low engine RPM, in agreement with the frequency criteria given above.

Field Experience with Automatic Engine/Transmission Control for a Farm Tractor

ABSTRACT AN automatic system received driver input on desired forward speed, while automatically sensing tractor load in terms of engine rpm decrease. The system then controlled governor setting and transmission ratio with the objective of delivering the desired forward speed while having the engine operate at high torque levels a maximum proportion of the time in order to achieve high fuel efficiency. The system functioned as designed, but no fuel savings or performance increases were found in heavy tillage operations as compared with manual control by skilled operators. Special system characteristics were found necessary to permit satisfactory automatic operation during conventional tillage procedures.

Start-of-lgnition Sensor for a Diesel Engine

Abstract A probe containing both an ionization sensor and a luminosity sensor was installed in place of a glow plug in both an Oldsmobile and a Volkswagen diesel engine in order to evaluate these two devices as “start-of-ignition” markers. Information on ignition delay relative to injection timing might well be the key item in fuel scheduling to effect maximum fuel efficiency and reduced exhaust emissions. The results indicated that at low engine RPM both sensors responded simultaneously, but at high RPM, independent of load, there was a noticeable and repeatable delay of the ionization gage signal. Also, the ionization sensor signal showed larger cycle-to-cycle variations in both shape and peak amplitude than the luminosity sensor making application of that signal to produce a reliable marker more difficult. The luminosity sensor showed consistent behavior under all test conditions.

Winter rape oil fuel for diesel engines: Recovery and utilization

AbstractAlthough vegetable oil cannot yet be recommended as a fuel for general use, considerable progress in recovery and use of rapeseed oil (Brassica napus L.) for diesel operation has been made. Operation of a small‐scale screwpress plant (40 kg/hr) was demonstrated. Maintenance of screw and end rings was a major problem. The plant has operated with a recovery efficiency of 77% and has processed 10,100 kg of seed in 230 hr. High viscosity of the rapeseed oil and its tendency to polymerize within the cylinder were major chemical and physical problems encountered. Attempts to reduce the viscosity of the vegetable oil by preheating the fuel were not successful in sufficiently increasing the temperature of the fuel at the injector to be of value. Short‐term engine performance with vegetable oils as a fuel in any proportion show power output and fuel consumption to be equivalent to the diesel‐fueled engines. Severe engine damage occurred in a very short time period in tests of maximum power with varying engine rpm. Additional torque tests with all blends need to be conducted. A blend of 70/30 winter rape and No. 1 diesel has been used successfully to power a small single‐cylinder diesel engine for 850 hr. No adverse wear, effect on lubricating oil or effect on power output were noted.

Noise Transmission and Control for a Light Twin-Engine Aircraft

One of the dominant source-path combinations for cabin noise in light twin-engine aircraft is propeller noise being transmitted through the fuselage sidewall. This source-path was investigated and candidate sidewall add- on treatments were installed and tested using both an external sound source and the propeller in ground static engine runs. Results indicate that adding either mass or stiffness to the fuselage skin would improve sidewall attenuation and that the honeycomb stiffness treatment provided more improvement at most frequencies than an equal amount of added mass. It is proposed that double-wall construction in conjunction with skin stiffening should provide a good weight-efficient combination for the aircraft studied. NE of the principal source-path combinations of cabin noise in light, twin-engine aircraft is propeller noise transmitted through the fuselage sidewall. Improved methods of controlling this cabin noise are needed to provide a comfortable passenger environment, while at the same time controlling aircraft weight and fuel consumption. Lighter weight noise control methods are needed to replace traditional approaches which have relied largely on relatively heavy damping and mass treatments. A number of approaches have been investigated for reducing cabin noise for this type of aircraft. Flight tests indicated interior noise can be reduced about 3.5 dB(A) by a reduction of engine rpm in an aircraft with variable pitch propellers.1 Design of propeller configurations is being in- vestigated as a means of reducing the noise generated at the source.2 Theoretical prediction methods for sidewall noise transmission have been developed to aid the search for noise- resistant sidewall structures. Theoretical analysis of interior noise transmission has included mechanical analogy models, rigid-stiffener/flexible-panel models, and more complex flexible-stiffener/flexible-panel models. 35 The analyses have been compared with laboratory test data for verification and have been used to examine a number of candidate noise control treatments including variations of skin thickness, stiffener stiffness, and structural damping, and addition of damping, mass, and honeycomb panel stiffening. Previous work has not included evaluation of candidate noise control treatments in an experimental situation using an actual aircraft. Such studies are needed to evaluate and compare candidate treatments, and to guide further development of noise control treatments. The purpose of this paper is to describe an experimental program of evaluation of three noise control treatments. The work is focused on added stiffness in the form of honeycomb panels. Also, two mass treatments are included for comparison. The tests were carried out using a light twin-engine aircraft (Fig. 1). Can- didate treatments were developed using the aircraft with a horn noise source in the laboratory. The performance of the stiffness treatment was verified using ground static runs of the aircraft engines. The laboratory portion of this investigation is described in Ref. 6.

Study of gear oscillations by the method of holographic interferometry

1. Investigation of the vibration modes and frequencies of a gear by the holographic method with broad variation in its geometric parameters made it possible from the practical standpoint to construct a system from resonance with respect to a three-node diametric vibration mode in the working range of engine rpm. 2. The experimental data cited make it possible to evaluate the accuracy of existing methods of computation, and also to correct them to obtain valid mathematical models.

Characteristics of Propeller Noise on an Aircraft Fuselage

Exterior noise was measured on the fuselage of a twin-engine, light aircraft at four values of engine rpm in ground static tests and at forward speeds up to 36 m/s in taxi tests. Propeller noise levels, spectra, and correlations were determined using a horizontal array of seven flush-mounted microphones and a vertical array of four flush-mounted microphones in the propeller plane. The measured levels and spectra are compared with predictions based on empirical and analytical methods for static and taxi conditions. Trace velocities obtained from point-to-point correlations are used to describe the propagating and rotating characteristics of the propeller noise field on the fuselage.