Effect of carrier gas pressure on vapor condensation and mass flow-rate in sonic nozzle

Laser machining efficiency and quality are closely related to gas pressure, nozzle geometry, and standoff distance. Modeling studies of laser machining rarely incorporate gas effects in part because of the complex structure and turbulent nature of jet flow. In this paper, the interaction of a supersonic, turbulent axisymmetric jet with the workpiece is studied. Numerical simulations are carried out using an explicit, coupled solution algorithm with solution-based mesh adaptation. The model is able to make quantitative predictions of the pressure, mass flow rate as well as shear force at the machining front. Effect of gas pressure and nozzle standoff distance on structure of the supersonic shock pattern is studied. Experiments are carried out to study the effect of processing parameters such as gas pressure and standoff distance. The measured results are found to match and hence validate the simulations. The interaction of the oblique incident shock with the normal standoff shock is found to contribute to a large reduction in the total pressure at the machining front and when the nozzle pressure is increased beyond a certain point. The associated reduction in flow rate, fluctuations of pressure gradient and shear force at the machining front could lower the material removal capability of the gas jet and possibly result in a poorer surface finish. The laser cutting experiments show that the variation of cut quality are affected by shock structures and can be represented by the mass flow rate. [S1087-1357(00)01702-0]

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Application of modelling approaches of twin-screw compressors: thermodynamic investigation and reduced-order model identification

E3S Web of Conferences ◽

10.1051/e3sconf/202131205001 ◽

2021 ◽

Vol 312 ◽

pp. 05001

Author(s):

Edoardo Di Mattia ◽

Agostino Gambarotta ◽

Mirko Morini ◽

Costanza Saletti

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Gas Pressure ◽

Operating Conditions ◽

Simplified Model ◽

Computational Time ◽

Discharge Temperature ◽

Twin Screw ◽

Shaft Power

Refrigeration is an essential part of the food chain. It is used in all stages of the chain, from industrial food processing to final consumption at home. In these processes, mechanical refrigeration technologies are employed, where compressors increase gas pressure from evaporation to condensation. In industrial refrigeration systems, twin-screw compressors represent the most widely used technology. A detailed mathematical model of a twin-screw compressor has been developed in Simulink® using differential equations for energy and mass balances to simulate the compression cycle that includes suction, compression and discharge phases. Gas pressure and enthalpy can be calculated as time functions during the cycle. However, the computational times obtained limit the possibility to extend the use of the model in the development of control strategies for the whole refrigeration plant in its real operating conditions. Therefore, the detailed model has been used to train a simplified model developed in Matlab®: the simulated mass flow rate, shaft power and the fluid discharge temperature have been employed to identify several geometrical and thermodynamic parameters of the simplified model. The latter relies on non-linear algebraic equations and, thus, requires a very short computational time. A limited performance dataset has been used to train the model, and a different dataset to test it: the results of the models have been compared, and small errors in mass flow rate, shaft power and fluid discharge temperature have been observed.

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Thermal effect on mass flow-rate of sonic nozzle

Thermal Science ◽

10.2298/tsci151104146d ◽

2018 ◽

Vol 22 (1 Part A) ◽

pp. 247-262 ◽

Cited By ~ 1

Author(s):

Hong-Bing Ding ◽

Chao Wang ◽

Gang Wang

Keyword(s):

Thermal Effect ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Sonic Nozzle

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Computational Analysis of a Diesel Engine Autoignition, Combustion, and Emissions Using Injection Rate Shapes

Volume 1: Large Bore Engines; Advanced Combustion; Emissions Control Systems; Instrumentation, Controls, and Hybrids ◽

10.1115/icef2013-19060 ◽

2013 ◽

Author(s):

Amit Shrestha ◽

Ziliang Zheng ◽

Tamer Badawy ◽

Naeim A. Henein

Keyword(s):

Diesel Engine ◽

Heat Release ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Computational Analysis ◽

Injection Rate ◽

Gas Pressure ◽

Operating Conditions ◽

Rate Of Heat Release

Injection rate shaping is a method used to control the instantaneous mass flow rate of the fuel during an injection event. The rate at which the fuel is delivered affects the composition of the combustible mixture and its distribution in the combustion chamber, thereby has an impact on the combustion process in the diesel engine. This paper investigates the effects of five different types of injection rate shapes on diesel engine autoignition, combustion, and engine-out emission trends using a three-dimensional computational simulation approach. For this purpose, an n-heptane fuel model is utilized. Initially, a tophat rate-shape, characterized by the constant mass flow rate of the fuel, is assumed to represent the actual injection profile of an actual engine. Then, in order to develop sufficient confidence in the simulation predictions, this assumption together with the calibrated CFD models are validated by reproducing the cylinder gas pressure, the rate of heat release, and engine-out emissions trends for two sets of engine operating conditions. Later, using all the rate shapes the investigation is conducted for one test point considering two different cases of fuel injection: Case 1 - same SOI and duration of injection (DOI), and Case 2 - same combustion phasing and DOI. The results obtained from the computational analysis show that the injection rate shape affects the autoignition, combustion, and emissions of a diesel engine. It is observed that the rate shapes, characterized by high injection rates at the beginning of the injection event, enhance the formation of negative temperature coefficient (NTC) regime. Therefore, the mole fractions of different species are determined during the NTC regime in order to examine the processes relevant to the formation of the NTC regimes for these rate shapes. Further, for the same SOI and DOI case, significant differences in the ignition delays between each rate shapes are observed. The maximum deviation of the ignition delay from the reference tophat is found to be 37%. Furthermore, the paper highlights the differences in the cylinder gas pressure, gas temperature, and rate of heat release due to different fuel delivery rates of different rate shapes. Finally, the comparison of the engine-out emissions for different rate shapes for both the cases of injection are presented and discussed in detail.

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ANALISIS KEKUATAN PEGAS PRESSURE REDUCER SEBAGAI PENURUNAN TEKANAN PADA MESIN DUEL FUEL

INVOTEK Jurnal Inovasi Vokasional dan Teknologi ◽

10.24036/invotek.v17i2.68 ◽

2017 ◽

Vol 17 (2) ◽

pp. 31-38

Author(s):

Dori Yuvenda ◽

Bambang Sudarmanta ◽

Erzeddin Alwi

Keyword(s):

Natural Gas ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Gas Pressure ◽

Dual Fuel ◽

Compressed Natural Gas ◽

Fuel Model

Pressure reducer merupakan komponen utama pada conversion kit pada mesin bahan bakar ganda (duel fuel engine) yang berfungsi sebagai penurun tekanan pada bahan bakar compressed Natural gas dari tangki sebesar ± 250 bar menjadi tekanan kerja pada injektor gas sebesar ± 2 bar, sehingga menyebabkan kekurangan pasokan jumlah bahan bakar dari pressure reducer yang berpengaruh tethadap penurunan performa mesin, baik pada saat perubahan putaran mesin secara tiba-tiba maupun perubahan beban mesin. Mengatasi permasalah tersebut maka diperlukan upaya untuk meningkatkan performa pressure reducer agar lebih adaptif terhadap perubahan kondisi mesin. Salah satu upaya yang dilakukan untuk peningkatan performa tersebut adalah menambah kekuatan konstanta pegas pada area chamber stage dua pressure reducer. Penelitian ini menggunakan mesin Diamond tipe DI 800 dengan sistem dual fuel model indirect injection. Metode yang dilakukan adalah menvariasikan kekuatan konstanta pegas (25,55 N/m, 26,55 N/m, dan 27,55 N/m). Hasil terbaik didapatkan pada konstanta pegas 27,55 N/m terjadi peningkatan jumlah laju aliran gas (mass flow rate) pada saluran keluar (outlet gas pressure reducer) sebesar 7,42%. Hal ini menunjukkan terjadi peningkatan performa pressure reducer pada saat penambahan kontanta pegas pada stage dua

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