Effects of Dilution and Nozzle Diameter on Laminar Dimethyl Ether Lifted Flames

2013 ◽  
Author(s):  
Jie Zhou ◽  
Yuhua Ai ◽  
Wenjun Kong
Keyword(s):  
Mass Flow Rate ◽  
Dimethyl Ether ◽  
Mole Fraction ◽  
Flow Rate ◽  
Nozzle Exit ◽  
Nozzle Diameter ◽  
Nitrogen Dilution ◽  
Lifted Flames ◽  
Inner Diameter ◽  
Jet Velocity

This work aimed at studying the effects of nitrogen dilution and nozzle exit inner diameter on the liftoff properties of the dimethyl ether (DME) jet diffusion flames. The liftoff properties including the liftoff position (HL), the critical liftoff velocity (Ulo) and the critical blowout velocity (Ubo) were studied experimentally. In nitrogen dilution experiments, a slowly converging nozzle was used with inner exit diameter of 0.43 mm. When mole fraction of N2 (Z) increased, a) HL increased because the dilution reduced the chemical activity of fuel, in order to achieve stoichiometric conditions, the stabilization point of the lifted flame moved downstream. b) at the critical liftoff condition, the flow rate of DME decreased with the increase of N2, while the total flow rate was almost unchanged, so the jet velocity was almost the same. c) as Z increased, the stabilization zone of the DME liftoff flames became narrow and small. In the experimental study of the effects of the nozzle diameter on the flame liftoff characteristics, six nozzles with i.d. of 0.17mm, 0.25mm, 0.386mm, 0.43mm, 0.693mm and 1.152mm were used. These nozzles had different materials and nozzle exit types. The experimental results showed that the nozzle inner diameter has a significant impact on the flame liftoff characteristics. As the nozzle diameter increased, four types of different liftoff features were observed. The flame was blown out directly with i.d. of 0.17 mm. The DME flame could only be observed liftoff by ignition at a proper position downstream with i.d. of 0.25 mm, 0.386 mm and 0.43 mm. The observations are agreed with that reported in the literatures. While it could be lifted off directly by increasing the mass flow rate of fuel/dilution with i.d. of 0.693 mm. This is the new observation in the present work. It is different from the report in the literatures that the DME flame could not be lifted off directly by increasing the jet velocity except for far field ignition at relatively low mass flow rate. When the nozzle i.d. was increased to 1.152 mm, the DME flames could be lifted off by three different methods: increasing the flow rate of fuel/dilution, decreasing the flow rate of the fuel and ignition the flame downstream. Oscillation lifted DME flames were found with i.d. of 1.152 mm when the fuel was highly diluted by nitrogen. The experimental results also showed that the critical liftoff velocity Ulo and the critical blowout velocity Ubo were strongly dependent on the inner diameter, which decreased with the increase of the nozzle diameter. When the jet velocity was kept constant, the flame liftoff height HL increased with the increase of the nitrogen mole fraction Z for all lifted flames.

The Liftoff Properties of Dimethyl Ether Jet Diffusion Flames With Preheating

2013 ◽  
Author(s):  
Jie Zhou ◽  
Yuhua Ai ◽  
Wenjun Kong
Keyword(s):  
Ambient Temperature ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Diffusion Flames ◽  
Thermal Buoyancy ◽  
Jet Diffusion Flames ◽  
Lifted Flames ◽  
Low Mass ◽  
Jet Velocity

Liftoff properties of DME laminar axisymmetric diffusion flames were investigated experimentally with emphasis on the preheating effects. At room temperature, DME presented a different liftoff phenomenon from the non-oxygenated hydrocarbon fuels. It could not be lifted off directly by increasing the jet velocity except for far field ignition at relatively low mass flow rate. When fuel and dilution were preheated, the DME flame could be lifted off directly by increasing the jet velocity. The range of the mass flow rate of stabilized DME liftoff flames became much narrower and the liftoff height became much smaller at fuel preheating than that at ambient temperature. With the increase of the jet temperature, the DME liftoff flames exhibited as one of the following three types: stationary lifted flames, stable oscillating lifted flames and unstable oscillating lifted flames. Stationary lifted flames existed when the initial temperature was relatively low (less than 350 K). Stable oscillating lifted flames were observed at relatively high preheated temperature (about 350 K ∼ 750 K), and the trajectory of the liftoff flame base was nearly sinusoidal. Both the oscillating frequency and amplitude increased with the preheating temperature. The oscillating lifted flames were caused by thermal buoyancy effect, inertia and the instability in the inner flow. When the jet temperature exceeded 750 K, the oscillating lifted flames became unstable and easily to be blown out. The flame base of the stabilized DME liftoff flame had a tribrachial structure at both ambient temperature and elevated temperature.

Theoretical Description of a New Method of Optimal Program Design

1981 ◽  
Vol 21 (04) ◽  
pp. 425-434 ◽  
Author(s):  
Stefan Miska ◽  
Pal Skalle
Keyword(s):  
Reynolds Number ◽  
Objective Function ◽  
Flow Rate ◽  
Program Design ◽  
Impact Force ◽  
Nozzle Diameter ◽  
General Description ◽  
Rate Of Penetration ◽  
Jet Impact ◽  
Jet Velocity

Abstract Drilling hydraulics have considerable effect on the rate of penetration. Previous studies have examined this problem; however, the effects of differential pressure and reliability of pumping equipment usually were neglected. This paper gives a general description of hydraulic drilling parameters optimized when both these effects were considered. To derive the necessary conditions for optimal hydraulics a nonlinear programming method was applied. Introduction In the rotary drilling process the rock must be fractured at the bottom of the hole. To allow further fracturing and drilling progress, the cuttings must be removed from the bottom efficiently and transported toward the surface. For these purposes, both mechanical and hydraulic energy are brought from the surface to the rock face and should be applied in optimal manner. Previous work in drilling hydraulics has established that this has considerable influence on the rate of penetration as well as on other indicators of drilling efficiency. For that reason, this topic has been a subject of several investigations, both theoretical and experimental. Optimal hydraulics is the proper balance of hydraulic elements that satisfy some criterion of estimation (the objective function). For given drilling fluid properties, these parameters are flow rate (q) and equivalent jet bit nozzle diameter (de). Hydraulic quantities commonly used to characterize jet bit performance include hydraulic horsepower, jet impact force, jet velocity, and Reynolds number at the bit nozzles. However, all these hydraulic quantities are determined when the flow rate and equivalent nozzle diameter have been established. Briefly, the methods of optimal hydraulics program design can be divided in two groups:methods which depend on determining the bottomhole cleaning required, usually bit hydraulic horsepower, to balance the mechanical energy level, andmethods which assume maximization of an arbitrarily established criterion of estimation. Methods in Group 1 have limited application during drilling program design since the required level of hydraulic horsepower, for given mechanical parameters (weight-on-bit and rotary speed combinations) in a particular formation interval, require field tests and thus they cannot be applied before drilling. This method is indicated in Fig. 1. Fullerton has balanced the mechanic and hydraulic energy by means of the "constant drilling energy" concept, valid for some formation types. The various criteria to be maximized in Group 2 are hydraulic horsepower, jet impact force, jet velocity, and Reynolds number. The basic work on this topic was published by Kendall and Goins. Methods for selecting proper nozzle sizes and flow rams are given for each criterion of estimation except the Reynolds number. The latter criterion is discussed by other authors, but they discussed optimal flow rates and equivalent nozzle diameter only for the constant pump pressure range. It was shown that using maximum Reynolds number at the bit nozzles as an objective function for optimal hydraulic program design gives the same result as for maximum jet impact force. SPEJ P. 425^

Evaluation of Mass Flow Rate Distribution in Diesel Fuel Spray by L2F

2011 ◽  
Author(s):  
Keisuke Komada ◽  
Noritsune Kawaharada ◽  
Daisaku Sakaguchi ◽  
Hironobu Ueki ◽  
Masahiro Ishida
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Diesel Fuel ◽  
Nozzle Exit ◽  
Evaluation Method ◽  
Fuel Spray ◽  
Orifice Diameter ◽  
Dense Region ◽  
Fuel Mass

A laser 2-focus velocimeter (L2F) has been applied for measurements of velocity and size of droplets of diesel spray and an evaluation method of mass flow rate has been proposed. The L2F has a micro-scale probe which consists of two foci. The distance between two foci is 17μm. The data acquisition rate of the L2F has been increased to 15MHz in order to capture every droplet which appears in the measurement volume. The diesel fuel spray injected intermittently into the atmosphere was investigated. The orifice diameter of the injector nozzle was 0.113mm. The injection pressure was set at 40MPa by using a common rail system. Measurements were conducted on ten planes 5 to 25mm downstream from the nozzle exit. It was clearly shown that the velocity of droplet was the highest at the spray center. The size of droplet at the spray center decreased downstream within 15mm from the nozzle exit. The mass flow rate near the spray center was found to be larger than that in the spray periphery region. It was confirmed that the fuel mass per injection evaluated by the proposed method based on the L2F measurement was near to the injected mass in a plane further than 15mm from the nozzle exit. However, fuel mass was underestimated in a plane closer to the nozzle exit. The probability density of infinitesimal distance between surfaces of adjacent droplets increased remarkably near the spray center 5 and 12mm downstream from the nozzle exit. As infinitesimal distance can be thought as an indicator of a highly dense region, it is understood that underestimation of fuel mass near the nozzle exit is due to the highly dense region. The diameter of the region, where the highly dense region was observed, was estimated as an order of 0.2mm in a plane 5mm downstream from the nozzle.

scholarly journals Modelling of non-stationary pressure fluctuations during boiling in a minichannel

2019 ◽  
Vol 128 ◽  
pp. 04007 ◽  
Author(s):  
Romuald Mosdorf ◽  
Hubert Grzybowski ◽  
Iwona Gruszczyńska
Keyword(s):  
Experimental Data ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Fluctuations ◽  
Evaporation And Condensation ◽  
Proposed Model ◽  
Low Mass ◽  
Inner Diameter ◽  
Periodic Changes

Boiling in a minichannel occurring at a low mass flow rate is accompanied by non-stationary twophase flow. The analysis of pressure fluctuations during non-stationary boiling in minichannel shows that quasi-periodic changes in flow patterns can be observed in such fluctuations. We can define in such a way the sequences, which are called “oscillating boiling patterns”. In the present paper the model, which allows us to simulate the appearance of “oscillating boiling patterns” has been presented. In the proposed model the mass flow rate changes (because of evaporation and condensation) are modelled by compressible volumes representing various sizes bubbles. In the paper the good quality agreement between experimental data and simulation results has been achieved. Experimental data was collected during the boiling in open minichannels system with inner diameter of 1 mm.

Flexible Joule-Thomson Micro-Refrigerator

2009 ◽  
Author(s):  
M. Kohno ◽  
A. Tanabe ◽  
Y. Kuwamoto ◽  
H. Kubota ◽  
Y. Takata
Keyword(s):  
Heat Exchanger ◽  
Numerical Analysis ◽  
Mass Flow Rate ◽  
Flow Rate ◽  
Cooling Power ◽  
Temperature Profiles ◽  
Evaporator Temperature ◽  
Cooling Performance ◽  
Inner Diameter ◽  
Outside Diameter

In this study, a prototype flexible Joule-Thomson micro-refrigerator was fabricated and its cooling power was examined. The micro-refrigerator uses N2, C2H4 or CO2 as a working gas and it consists mainly of a heat exchanger and an evaporator. The outside diameter of the heat exchanger outer tube is 0.9 mm and that of the inner tube is 0.4 mm. The length of the heat exchanger is 450mm. The inner diameter of the evaporator capillary is 0.1 mm. A cooling power of 100 mW at an evaporator temperature of 277 K was attained for inlet and outlet gas (CO2) pressures of 5.0 MPa and 0.1 MPa, respectively. To understand the cooling performance, a numerical analysis of the heat exchanger has been done and the effects of mass flow rate and dimensions of the heat exchanger on temperature profiles and effectiveness were examined.

Study on Flow Characteristics of NGV Injectors Using Plungers with Varied Inner Diameters

2019 ◽  
Vol 390 ◽  
pp. 91-98
Author(s):  
Tae Jun Yoon ◽  
Kwon Se Kim ◽  
Doo Seuk Choi
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Gas Flow ◽  
Flow Characteristics ◽  
Velocity Variation ◽  
Injection Nozzle ◽  
Design Variables ◽  
Point Injection ◽  
Inner Diameter

In this study, a plunger and injection nozzle were designed to improve the injector used in multi-point injection NGV engines. The purpose of this study is to analyze the pressure and velocity characteristics of the injector plunger and show mass flow rate trends for the gas injected from the nozzle. Using the ANSYS program, a new injector was modeled according to applicable design variables, and the gas flow into the plunger was visualized. In addition, methane fuel was used in the simulation, and the inlet and outlet of the injector were applied with 8 bars pressure and opening conditions. As a result, in the model with a 1.2 mm inner diameter plunger valve, the mass flow rate of gas injected from the injection nozzle was stable from 0.075 mm to 0.2 mm, and it was possible to reduce the velocity variation and pressure generated inside the plunger.

Analysis of Radiation Performance for a Combustion-End Radiator of a TPV System

2013 ◽  
Vol 448-453 ◽  
pp. 1353-1358
Author(s):  
Lei Wang ◽  
Ye Xin Xu ◽  
Rui Ming Yuan ◽  
Xi Wu ◽  
Xiao Jie Xu
Keyword(s):  
Mass Flow Rate ◽  
Power Density ◽  
Mass Flow ◽  
Flow Rate ◽  
Combustion Efficiency ◽  
Complete Combustion ◽  
Air Mass ◽  
Average Temperature ◽  
Inner Diameter ◽  
Radiator System

In this paper, the authors analyzed effects of the factors, such as the air mass flow rate, the geometric dimensioning of the inner and outer combustion tubes and the thickness of the radiator, to the performance of the combustion-end radiator system. The result shows that optimal performance will be achieved when the combustion power is 1kW and the air mass flow rate is 5 times higher than the requirement for the complete combustion of CH4. On this basis, the effect of the geometric dimensioning to the combustion-radiator system is discussed. The performance of the combustion-radiator system is the best when the inner diameter of inner tube is 24mm, the length of the combustion tube is 40mm and the radiator thickness is 1mm. In this condition, the average temperature of the radiant surface, the radiant power density of the radiator and the combustion efficiency are 1530K, 9.41W/cm2 and 47.3%, respectively.

Effects of Jet Dilution and Co-Flow on Sooting Characteristics of Hydrocarbon Fuels

2001 ◽  
Author(s):  
S. F. Goh ◽  
S. Kusadomi ◽  
S. R. Gollahalli
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Critical Mass ◽  
Hydrocarbon Fuels ◽  
Nitrogen Flow Rate ◽  
Fuel Flow Rate ◽  
Radiation Emission ◽  
Fuel Flow ◽  
Nitrogen Dilution

Abstract A study was conducted to understand the effects of dilution and co-flow on the sooting characteristics of hydrocarbon fuels. Measurements of the critical mass flow rate of a fuel at the threshold of smoking and the mass flow rate of the dilution gas (nitrogen) required to suppress smoking at several fuel flow rates were obtained. At the same time, the radiation emission and flame heights were also measured. Also recorded was the axial radiation profile at the critical fuel mass flow rate. Three fuels of differing sooting propensities were used: ethylene (C2H4), propylene (C3H6), and propane (C3H8). A 3.2 mm ID burner was employed. The results showed that propylene had the highest critical fuel flow rate and the highest nitrogen dilution required to suppress smoking, followed by ethylene and propane. Besides, propylene produced the highest flame radiation, followed by ethylene and propane. The variation of nitrogen flow rate required for smoke suppression with fuel flow rate exhibited a skewed bell shape for all fuels. The co-flow had no significant effect on flame soot liberation characteristics.

Delay in Flow Separation for Circulation Controlled Cylinders

2010 ◽  
Author(s):  
Byron W. Patterson ◽  
Gerald M. Angle ◽  
Emily D. Pertl ◽  
James E. Smith
Keyword(s):  
Wind Tunnel ◽  
Mass Flow Rate ◽  
Flow Rate ◽  
Separation Point ◽  
Radius Of Curvature ◽  
Circulation Control ◽  
Point Location ◽  
Trailing Edge ◽  
Edge Radius ◽  
Jet Velocity

Recent circulation control testing at West Virginia University, in a closed loop wind tunnel, has been conducted on models where the trailing edge radius was selected to be smaller than that used in literature, such as Loth and Boasson [1], 1.5 inches and Englar [2], 0.4375 inches. The reduced size was chosen in an attempt to minimize the drag experienced during periods of non-activation of the circulation control, and the smaller size was more compatible to the wind tunnel test section size. However, while the drag is lessened by a smaller trailing edge, the performance of circulation control also appears to be dependent upon a multitude of variables including, but not limited to, the trailing edge radius and jet velocity. Through a modeled experiment, the two attributes that influence the circulation control performance were concurrently manipulated by varying the radius of curvature and the velocity of the blown jet. The combination of these characteristics were experimentally explored to determine the location where the jet leaves the surface of the cylinder, also known as the separation point. The optimum separation point is defined as the farthest angular displacement from the plane of the blown jet exit slot, which corresponds to the greatest increase in the circulation around the cylinder, representing the trailing edge of a circulation control airfoil. From the known radius and jet velocity, an expression that relates the separation point and the mass flow rate velocity quantity are compared. Understanding the blowing coefficient and its impact on the separation point, results in a predictive relationship between these two attributes of circulation control. The results of this two-dimensional cylinder study found that an increase in trailing edge radius decreased the location of the separation point. In addition, an increase in the jet velocity resulted in an increase in the separation point location. The combination of these two quantities produced a relationship similar to each individually, illustrated by the mass flow rate velocity value, which is the blowing coefficient excluding free stream conditions, versus the angle of separation. Data is therein compared to the theory by Newman [3], which predicts a maximum separation point location at 245 degrees beyond the jet exit plane and an increase in the separation point as the radius of curvature increases. The results of this study found a separation point maximized at 231 degrees, and, contrary to Newman [3], a decrease in the separation point was found as the radius of the cylinders increased.

Sign in / Sign up

Export Citation Format

Share Document