Exhaust Pipe Length Research Articles

A One-Dimensional Numerical Model for High-Performance Two-Stroke Engines

Computer software that simulates the thermodynamic and gas dynamic properties of internal combustion engines can play a significant role in the design and optimization of internal combustion engines. In the present work, a quasi-dimensional numerical model for two-stroke engines is presented. Particular attention was paid to reporting in-cylinder models, combustion (turbulent with flame development and flame–wall interaction), and turbulence (K-k-ϵ model), with the addition of tumble- and squish-generated turbulence that is quite common in such engines. The aim was to reduce the role of the calibration constants, which are fundamental for correlating the models with the experiments, and relations for calculating the tumble ratio and turbulent scales were reported. A one-dimensional model for manifolds is also presented (solving the Euler equations), using the second-order Roe Riemann solver with some improvements, paying particular attention to the source terms, such as area variation. Additionally, a new approach to the end-pipe boundaries, which would reduce the mass conservation error, is reported. The engines tested were two kart two-stroke engines, used for racing purposes: the IAME X30 engine and the IAME Screamer III KZ engine. A comparison between the model results and the experimental data was made, and good accordance was observed, with a root mean square error of about 0.5 kW and providing good accuracy in evaluating changes, such as the combustion chamber squish area and the exhaust pipe length.

Research on Tail Pipe for Engine Performance and Exhaust Noise

The whole engine model，including intake system, coupling with exhaust system, is established by the software GT-POWER. Through the parameter change of tail pipe geometry, it is analyzed in this paper how the tail pipe geometry affect tail pipe noise. With the test data and the simulation calculation results, it analyses the influence of the tail exhaust pipe length, diameter, shape, terminal bending angle on engine performance and tail pipe noise, so as to choose suitable design parameter of tail pipe to meet the requirements of engine performance and the tail pipe noise.

Acoustic characterization of a partially-premixed gas turbine model combustor: Syngas and hydrocarbon fuel comparisons

In this work, the acoustic behavior of a combustion instability in a gas turbine model combustor was investigated as fuel properties, air flow rates, and burner geometry were varied. The dual-swirl burner, developed at DLR Stuttgart by Meier, was operated using syngas (H2/CO), ethylene, propane, and methane. The frequency of the instability was found to vary significantly from 250 to 480Hz. When the plenum volume and the exhaust pipe length and diameter were changed, the frequencies followed trends similar to a Helmholtz resonator. The variation of fuel type, flame speed, and air flow rate greatly altered the instability frequency and amplitude. These effects are not predicted by Helmholtz or organ tone acoustic theory. Higher frequencies were correlated with larger laminar burning velocities and higher air flow rates. The burner is a forced resonator, in which the flame oscillations couple with the flowfield to create convectively altered Helmholtz resonances. This suggests the need for an improved model of a forced Helmholtz resonator that includes flame properties. Alkane fuels displayed similar acoustic trends, but ethylene varied greatly from methane and propane. Syngas displayed different behavior than hydrocarbon fuels, even when the laminar flame speeds of the fuels were matched between ethylene and a syngas mixture. Flame characteristics such as anchoring, liftoff height, and shape appear to play a major role in the determination of instability strength and presence. With increasing hydrogen-content in the syngas-mixture, the flame transitions from a lifted to a fully anchored flame, resulting in a drastic decrease in the acoustic amplitude associated with non-resonating flames. Rayleigh indices show that flat flames create strong regions of thermo-acoustic coupling compared to axially extended V-shape flames. It is concluded that, in the current burner configuration, integrated-acoustics occur that involve a combination of Helmholtz and convective-mechanisms.

Mathematical Lens: Reflections

James Metz, a community college mathematics professor in Honolulu, Hawaii, took photograph 1 on a street corner in Tokyo in the Akihabara area, known as “electric town” (where electronics shops of all types are found). In the photograph, a mirrored curved column reflects the image of a passing delivery truck. Students can use a short length of chrome exhaust pipe or drainpipe and a small toy truck to model this photograph.

626 小型ガソリン機関を用いた燃料消費率におよぼす排気管長さの影響について(オーガナイズドセッション : 熱システム)

626 小型ガソリン機関を用いた燃料消費率におよぼす排気管長さの影響について(オーガナイズドセッション : 熱システム)

522 非定常燃焼とそれを利用した制御(GS-6 燃焼(3))

Characteristics of unsteady premixed combustion were observed in two cases, the first was the self-excited oscillating combustion and the second was the combustion under the forced oscillating supply of mixture. The field noise level near the exit of exhaust pipe was measured. Pressure fluctuations in combustion chamber and OH chemiluminescence from the combustion chamber were measured simultaneously in time series. In the case of short exhaust pipe length, combustion oscillation can be controlled by a forced oscillating mixture supply with specified frequency. Furthermore, no distinct peaks was identified in the power spectrum of pressure fluctuation when combustion oscillation was attenuated despite that two dominant peaks were obtained in the case of self-excited oscillating combustion.

Studies of helmholtz resonance in a swirl burner/furnace system

This paper describes and analyzes the combustion-excited Helmholtz resonance in a swirl burner/furnace system. Preliminary work showed the importance of variables such as air/fuel ratio, mode of fuel entry, and length of exhaust pipe attached to the exit of the furnace. Conditions were chosen (50% axial, 50% premixed natural gas and air, 600-mm-long exit pipe, air/fuel ratio=1.53) that gave a clean, near sinusoidal pressure signal at the furnace exit. This signal was used as a trigger to enable phase-averaged axial and tangential velocities as well as temperatures to be taken throughout the furnace and into the exit pipe. The results show that a lifted flame core region exists over all of the oscillation cycle. Combustion excitation via the Rayleigh criteria comes via a periodic combustion wave of annular form located next to the furnace wall. The minimum pressure of the resonance causes a large inflow into the furnace with well-known swirltype flow patterns, which extinguishes the annular wall flame. The central flame core boundary is located in a low-velocity region between the forward and reverse flow regions. Conversely, the peak resonant pressure virtually stops the inflow into the furnace from the burner and allows the annular wall flame to propagate backward into the furnace. Complex coherent structures in the tangential radial direction are formed close to the junction of the swirl burner and the furnace. The influence of the precessing vortex core (PVC) in the swirl burner exhaust in setting up the resonance seems to be small; however, it does appear to further excite the resonance to higher amplitudes when its frequency is close to that of the Helmholtz oscillation.

Effect of tailpipe reflections on resonator—muffler performance

The straight-through resonators are widely used as exhaust mufflers for ICE. They are characterized by high attenuation at and near the resonance frequencies. The tailpipe reflections severely affect the attenuation of this type of muffler. In this paper, equations are derived to illustrate the effect of tailpipe reflections on the muffler attenuation. Numerical examples are given to show these effects at different tailpipe lengths, different chamber volumes, and at various exhaust pipe diameters. Results showed that the exhaust pipe length affects the frequencies at which maximum and minimum attenuation occur, while the chamber volume and the pipe diameter affect the magnitude of attenuation as well as the periodicity of the attenuation curve. Analysis has been presented for the plane wave and for the general case where radial and angular modes exist. The results are useful for the design of a complete muffler—tailpipe exhaust system.

Effect of the Length of Exhaust Pipe on the Back Pressure and Brake Output of the Internal Combustion Engine

In this paper, the relation between the back pressure and the length of the exhaust pipe of small internal combustion engines was studied, and it was made clear that the value of the back pressure (i. e. the reading of the manometer) could be shown by a fluctuating curve of a definite pattern in accordance with the length of the exhaust pipe.

A Study on the Influence of Exhaust Pipe Length upon the Back Pressure Characteristics of an Internal Combustion Engine

A Study on the Influence of Exhaust Pipe Length upon the Back Pressure Characteristics of an Internal Combustion Engine

The Influences of the Inlet- and Exhaust Pipe Length on the Scavenging Performance of a Crankcase-Compressed Two Stroke Gasoline Engine

The Influences of the Inlet- and Exhaust Pipe Length on the Scavenging Performance of a Crankcase-Compressed Two Stroke Gasoline Engine

Exhaust Impulse Engine : 2nd Report, Other Cylinder Impulse Method and Installation

Concerning "Self cylinder impulse method", the 1st report was presented. "Other cylinder impulse method" is applied to 5, 6-and 7-cylinder engines, exhaust gas from all cylinders are exhausted into a common manifold, and the negative pressure ocurred in the manifold near top dead centre due to the exhaust impulse by the adjacent fired cylinder, is utilized to improve the scavenging efficiency. The volumetric efficiency, appling this method, increases up to about 100 %. Theoretical method for calculating pressure change in the manifold, including branch and connecting pipes, is developed. Design method and data for this method of engine are given. As an exhaust pipe length and sectional area affect pressure wave in exhaust pipe and an engine performance, a specially designed exhaust silencer in which an adjustable exhaust pipe is enclosed, and a special expansion tank should be installed when the exhaust impulse engine is actually installed.

Exhaust Impulse Engine : 1st Report, Self Cylinder Impulse Method

Many four-stroke diesel engines, whose output has been increased by about 15% over the conventional naturally aspirated engines basing on the so called "Exhaust Impulse Principle", have been manufactured. At present 150000 B.HP of these engines have been used without any particular trouble owing to application of this principle. There are two different methods to utilize exhaust pulse ; i.e. "Self cylinder impulse method" and "Other cylinder impulse method". The engine, to which the former is applied, has been equipped with exhaust pipes, and negative pressure occurs in the exhaust pipes during 120 deg-of crank revolution angle near top dead centre, the later utilizes the exhaust impulse caused by the adjacent fired cyinder. Theoritical brief method is developed for calculating the pressure change in the exhaust pipe. Design method and data, for the former type of engines and special expansion tanks to control exhaust pipe length, are given. Concerning the latter method, 2nd report is expected to be prepared.

Effect of Exhaust Pipe System upon the Performance Characteristics of a Two-Cycle Diesel Engine : (1st Report, The Influence of Exhaust Pipe Length)

This paper deals with the influence of the exhaust pipe length upon the performance characteristics of a two-cycle Diesel engine. The two-cycle uniflow scavenged three-cylinder Diesel engine was employed, and the length of each exhaust pipe was changed from 20 cm to 420 cm. The following results were obtained. (1) The optimum performance was obtained at the following pulsation coefficients q, i. e. q=0.24, 0.70 and 1.16, q being defined as q=nL/15c, where n : crankshaft revolutions per minute, L : length of the exhaust pipe and c : sonic velocity in the exhaust pipe. (2) Theoretical treatment performed by one of the present authors showed fair coincidence with the experimental results. (3) The difference of output developed by the engine at good tuning and that at poor tuning was about 15%. (4) In the practical application of the present results especially to the variable speed engines, a shorter optimum exhaust pipe length is preferable to the longer one.

Effect of Exhaust Pipe System upon the Performance Characteristics of a Two-Stroke Diesel Engine : 1st Report, The Influence of Pipe Length

This paper deals with the influence of the exhaust pipe length upon the performance characteristics of a two-stroke engine. The two-stroke uniflow scavenged three-cylinder diesel engine was employed, and the length of each exhaust pipe was changed from 20 cm to 420 cm. The following results were obtained. (1) The optimum performance was obtained at the following pulsation factors q, i.e. q=0.24, 0.70 and 1.16, q being defined as q=nL/15c, where n : engine revolutions per minute, L : length of the exhaust pipe and c : sonic velocity in the exhaust pipe. (2) Theoretical treatment performed by one of the present authors showed fair coincidence with the experimental results. (3) The difference of output developed by the engine at good tuning and that at poor tuning was about 15%. (4) In the practical application of the present results aspecially to the variable speed engines, a shorter optimum exhaust pipe length is preferable to the longer one.

Exhaust-Pipe Effects in a Single-Cylinder Four-Stroke Engine

The paper deals with an investigation of the fluctuations of pressure, due to piston motion on the exhaust stroke, which occur in the exhaust pipe of a single-cylinder four-stroke engine. Indicator diagrams of exhaust-port and of cylinder pressure, and measurements of air consumption were recorded, using exhaust pipes of three different diameters at three standard engine speeds; the exhaust pipe length was varied over a wide range in each case. In the light of the data thus obtained, the effects on air consumption of progressive alterations in valve timing were studied under known conditions of exhaust port pressure. Further trials were then carried out in which the valve timing which gave the maximum air consumption was determined for the full range of conditions of speed and exhaust pipe dimensions. The experimental results are discussed, and a method is derived by which the pressures in the exhaust port throughout the cycle may be obtained from theoretical considerations; the method is also directly applicable to induction pipe conditions.

Exhaust Systems of Two-Stroke Engines

Crankcase-scavenge two-stroke engines have always been fitted with a large expansion chamber immediately outside the exhaust ports, but this is by no means essential, as such engines will operate very satisfactorily with a plain exhaust pipe. The length of this pipe is most important and has a controlling influence on the scavenging of the cylinder and the performance of the engine. Even when an expansion chamber is used in the exhaust system, the length of exhaust pipe still has a very marked effect on engine performance. It has been found that certain arrangements of this combination of expansion chamber and pipes completely upset the performance of the engine, whilst others improve the performance, but it is possible to calculate the “equivalent length” of any system of this nature, and so arrange matters that the exhaust system is a help rather than a hindrance to the engine. Though certain results have not been satisfactorily explained, the tests carried out do give a fairly clear indication of the way in which the engine performance is affected by the variations in pressure in the exhaust system. The concluding section gives a description of the principle on which the self-induction engine works, and indicates how use is made of the pressure variations or oscillations in the exhaust pipe to scavenge the engine cylinder, resulting in the complete elimination of the air pump on a two-stroke engine.