Gas Flow In Nozzle Research Articles

An analytical and experimental investigation of the trajectories of particles entrained by the gas flow in nozzles

Among the parameters which determine the erosion damage sustained by the walls of a nozzle in which a mixture of gas and particles is flowing, is the angle between the direction of the particle flow and the wall surface at the moment of impact. In this work an approximate analytical solution is made for a number of gas particle flows to determine broadly the features on which particle trajectory depends and some experimental results are given which confirm the theoretical computations. It is shown that the divergent region of a conical nozzle is unlikely to suffer a severe particle attack but that for parallel flow convergent-divergent nozzles the convex region near the exit may be affected. The choke, on the other hand, is most susceptible to particle attack even by fairly small particles. It may be said, in general, that any particle which enters the choke section with a velocity which, in the absence of effects from the gas would allow the particle to strike the choke wall, will in fact hit the wall at some point along the length of the choke.

Exact solution op the Navier-Stokes equations for a compressible gas: PMM vol. 33, no. 1, 1969, pp. 152–157

The cases when an exact solution for the Navier-Stokes equation can be obtained, are of particular interest in investigations of the viscous fluid flows. Few such solutions are known for a viscous, heat-conducting gas flow in conical nozzle when the heat transfer at the wall is governed by a special law. It is also shown that such self-similar flows are absent in the case of a channel with plane walls. In the present paper we show that ni this case we can (under certain well defined conditions) reduce the Navier-Stokes equations to a system of ordinary differential equations whose solution can be obtained either in a closed form (provided that certain viscosity laws are observed) or numerically.

An analytical and experimental investigation of the velocities of particles entrained by the gas flow in nozzles

Among the parameters which determine the erosion damage sustained by the walls of a nozzle, in which a mixture of gas and particles is flowing is the speed attained by the particle before collision with the wall surface. This work is concerned with the determination of the particle velocity, and a number of relationships are given from which the variation in particle velocity can be obtained for a variety of gas conditions. The changes of state and velocity of the gas, occasioned by the interchange of heat and work between the gas and the particles are dependent on the ratio of the mass flow rate of particles to the mass flow rate of gas. It is shown that if this ratio is small the particle velocity may be obtained without serious error by assuming that the gas conditions are not affected by the presence of particles. Figures for the limiting value of this ratio for certain flows are given. The effects of particle size, density and initial relative velocity are investigated analytically and experimentally.

Calculation of mixed sub- and supersonic gas flow in a plane pressure nozzle

Plane vortex-free sub- and supersonic gas flow is considered without taking account of viscosity and heat conduction. For the system of equations of motion of the mixed elliptic-hyperbolic type in the potential plane, a particular solution is found which corresponds to gas motion in a nozzle with a curved sonic line. The system of equations used to construct the solution is neatly homogeneous, which made it possible to separate the principal part of the solution in the transonic region. The validity of the simplifications made is well confirmed by comparison with calculation, using the method of characteristics, and with experiment.

Experimental Research on Swirl Gas-Flow Heating Surface

A new type of heating surface, which is composed of swirl gas-flow nozzle at the entrance and single or double tube coils concentrically situated in the swirling gas flow, is introduced here. The features of this type are that, by changing the nozzle angle, the gas speed can be controlled indifferently to volumetric gas flow quantity, and that tubing does not need to be bend sharply. Several typical models of this heating surface system have been tested by a fundamental experimental set with electrically heated wire-coils and cooling air. The approximate relation between the Nusset number Nu and Reynolds number Re of tube is thus known to be : [numerical formula] where L, D0 are coil acial length and cylinder-diameter respectively and c is a constant changed by nozzle shape and nozzle exist angles. On the newly designed super-charged super-critical monotube boiler, two heating surfaces of this type were tried ; and their performance are reported here.

Diabatic Nozzle Flow with Constant Small Stage Efficiency

The concept of small stage efficiency is introduced when studying one-dimensional gas flow in nozzles in order to permit a closer approximation of real flow conditions than is possible from an isentropic analysis. It is more or less conventional to assume the flow conditions are adiabatic whenever the small stage efficiency is used. That is to say, small stage efficiency is generally considered in relation to flows contained within adiabatic boundaries, in which case it becomes a measure of the heat generated by internal frictional effects alone.

Compressible Gas Flow in Nozzle Taking Boundary Layer into Consideration : (Part 4, The Case of Fully Developed Laminar Layer, Experiments with Ring-Nozzle, and General Conclusion)

The longitudinal velocity and the pressure distribution of compressible gas flow passing through a small nozzle are mainly determined by the characteristic Reynold's Number RεN=(S2/L) (us0/v0) (us0, v0 are the local sonic speed and dynamic viscosity of gas before entering the nozzle respectively, S, L are the hydraulic radius and length of nozzle respectively) The cases for ReN>10 and 0.7<fb<1.4 (fb is the convergency of nozzle) were already covered by the previous reports of these series. In the present report, the remained case for ReN<10, where the fully developed boundary layers of both walls contact with each other as in the case of the Poiseuille's flow, is analysed theoretically. The flow coefficient, mean pressure, and the critical back pressure in this case are calculated and added to the results of previous reports to complete the full theoretical curves of the performance of nozzle flow. Experiments are conducted using a ring-nozzle with atomospheric air sucked by a steam ejector. Their results show good agreements to the theory. The main results are as follows : the change of mean pressure is not so steep against ReN, while the flow coefficient and critical back pressure show considerable decrease in the range of 10>ReN>0.5.

On gas flow in Laval nozzles

On gas flow in Laval nozzles

Compressible Gas Flow in Nozzle taking Boundary Layer into Consideration : Part 2 Calculations of Flow with Turbulent Layer, and Experiments of Pressure Distribution

The one dimensional theoretical calculations of compressible gas flow in nozzles accompanied by turbulent layer at the walls, are carried out in this paper using the similar methods to the case of laminer layer of Part 1. By theoretical consideration, the characteristic nozzle number for the case of turbulent layer is determined by Ω'=lν01/4/r5/4uso1/4 The experiments of pressure distrbutions of twenty simple nozzles are done, and analyzing their results, the foregoing theoretical results of the two reports are well proved in quality and quantities. The critical Reynold's number is estimated to be 104∼105, and in practice, the large nozzles more than about 10 mm dia, belong to the turbulent domain.