WO2006047069A2

WO2006047069A2 - Aspirator

Info

Publication number: WO2006047069A2
Application number: PCT/US2005/036216
Authority: WO
Inventors: Christopher L. Lanza
Original assignee: Carleton Technologies, Inc.
Priority date: 2004-10-07
Filing date: 2005-10-07
Publication date: 2006-05-04
Also published as: WO2006047069A3

Abstract

An aspirator for inflating inflatable aircraft emergency escape slides and life rafts has a combination of gas conduits with calculated dimensions to achieve an aspiration ratio of approximately 4.0.

Description

11836.113004

ASPIRATOR

TECHNICAL FIELD

The present invention relates to aspirators, and more particularly, to aspirators for inflating inflatable devices such as ai rcraft emergency slides and life rafts.

BACKGROUND OF THE INVENTION

Aspirators for inflating inflatable devices such as aircraft emergency slides and life rafts use a pressurized gas to entrain outside air to provide the volume of gases needed to inflate a slide or raft. In order to minimize the amount of stored pressurized gas needed for the raft or slide, the aspirator must efficiently entrain and mix the outside air with the stored gas.

The efficiency of the aspirator is defined by the aspiration ratio, which is the ratio of the total mass flow of primary plus entrained gases to the mass flow of the primary gas. Typical aspiration ratios for existing aspirators of this type are in the range of 2.4 to 2.6. It is a principal object of the present invention to provide as aspirator withi an aspiration ratio that is significantly higher than the aspiration ratios of prior art aspirators.

SUMMARY OF THE INVENTION

Briefly described, in a first embodiment is an aspirator for inflating an aircraft emergency slide or life raft having a base for receiving a pressurized gss inlet pipe and atmospheric pressure gas. A plurality of nozzles positioned inside the base and connected to the pressurized gas inlet pipe with outlets in a plane orthogonal to the atmospheric gas flow. A mixing tube attached to the base for receiving the combined pressurized gas and said atmospheric pressure gas wherein the combined pressurized gas and atmospheric pressure gas have a mass flow more that three times the mass flow of said pressurized gas.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become appreciated and be more readily understood by reference to the following detailed description in conjunction with the accompanying drawings, wherein:

FIG. 1 is a cross sectional side view of an aspirator according to the present invention;

FIG. 2 is a top view of the body of the aspirator of FIG. 1 showing the inlet pipe, manifold, manifold legs and nozzles of the aspirator;

FIG. 3a is two side views and top and bottom views of the body of the aspirator of FIG. 1 ;

FIG. 3b is a cross-sectional view of the side inlet to the body of the aspirator shown in FIG. 3a;

FIG. 4a is a perspective view of the mixing tube of the aspirator of FIG. 1 ;

FIG. 4b is a side view of the mixing tube of FlG. 4a; FIG. 4c is a cross sectional view of the mixing tube of FIG. 4a;

FIG. 5a is a perspective view of the inlet fairing of the aspirator of FIG. 1;

FIG. 5b is a top view of the inlet fairing of FIG. 5a;

FIG. 5c is a cross sectional view of the inlet fairing of FIG. 5a;

FIG. 6a is a perspective view of the manifold hub used in the aspirator of FIG. 1;

FIG. 6b is a top view of the manifold hub of FIG. 6a;

FIG. 6c is a side view of the manifold hub of FIG. 6a;

FIG. 6c is a cross sectional view of the manifold hub of FIG. 6a;

FIG. 7 is a top view of the manifold nozzle layout for the aspirator of FIG _ 1 ;

FIG. 8a is a perspective view of the manifold leg of FIG. 1 ;

FIG. 8b is a top view of the manifold leg of FIG. 8a; FlG. 8c is a cross sectional view of the manifold leg of FIG. 8a;

FlG. 9a is a perspective view of the nozzle of FIG. 1 ;

FIG. 9b is a cross sectional view of the nozzle of FIG. 9a

FIG. 10a is a perspective view of an alternative mixing tube to the mixing tube of FIG. 4a;

FIG. 10b is a side view of the mixing tube of FIG. 10a; and

FIG. 10c is a cross sectional view of the mixing tube of FIG. 10a.

It will be appreciated that for purposes of clarity and where deemed appropriate, reference numerals have been repeated in the figures to indicate corresponding features, and that the various elements in the drawings have not necessarily been drawn to scale in order to better show the features of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to Fig. 1 , a cross sectional side view of an aspirator 10, according to the present invention, includes a body 12, a mixing tube 14, an inlet fairing 16, a check valve flapper 18, a piston 20, a closing spring 22, an inlet pipe 24 for the pressurized gas, a manifold 26, two manifold legs 28, and a plurality of nozzles 30.

In operation, before the pressurized gas enters the inlet pipe 24, the closing spring 22 keeps the check valve flapper 18 covering the top opening of the inlet fairing 16. When pressurized gas enters the inlet pipe 24, the gas pressure allows the check valve flapper 18 to open, and the air entering through the inlet fairing 16 is entrained with the pressurized gas exiting from the nozzles 30 and passes through the mixing tube 14. FIG. 2 is a top view of the body 12 of the aspirator 10 showing the inlet pipe 24, the manifold 26, the manifold legs 28 and the nozzles 30.

The body 12 of the aspirator is shown in FIG. 3a and opening for the inlet pipe 24 is shown in FIG. 3b.

FIG. 4a is a perspective view of the mixing tube 14 with a side view shown in FIG. 4b and a cross sectional view shown in FIG. 4c.

A perspective view of the inlet fairing 16 is shown in FIG. 5b with top and cross sectional views shown in FIGs. 5b and 5c, respectively.

FIG. 6a is a perspective view of the manifold 26, with a top view shown in FIG. 6b, a side view shown in FIG. 6c and a cross sectional view shown in FIG. 6d.

FIG. 7 is a top view of the manifold nozzle layout for the aspirator 10 showing the placement of the manifold 26, the inlet tube 16, the manifold legs 28, and the nozzles 30 inside the body 12 of the aspirator.

A perspective view of the manifold leg 28 is shown in FIG. 8a. FIG.8b shows the end and top views, and FIG. 8c shows the cross sectional view of the manifold leg 28.

FIG. 9a is a perspective view of the nozzle 30 while FIG. 9b presents a cross sectional view.

FIG. 10a is a perspective view of a mixing tube 32 that is an alternative to the mixing tube 14. FIG. 10b is a side view and FIG. 10c is a cross sectional view of the mixing tube 32. FIG. 11a is a perspective view of a nozzle 34 that is an alternative to the nozzle 30. FIG. 11b is a cross sectional view of nozzle 34. The embodiment shown and described using the mixing tubes 14 or 32 and the nozzle 30 achieves an aspiration ratio of 4.0 which is a significant improvement over prior art aspirators. The critical dimensions to achieve this 4.0 ratio are the radius of the curve of the inlet fairing 16, the inside diameter of the bottom or flapper end of the body 12, the throat or smallest diameter of the nozzle 30, the inside diameter at the flared end of the nozzle 30, the throat or smallest inside diameter of the mixing tube 32 and the inside diameter at the top (exit) of the mixing tube 32. The aspiration ratio was calculated based on data entered for the throat and inside diameter of the flared end of the nozzle, the length or vertical height of the nozzle, the throat and inside diameters at the exit of the mixing tube 14, and the inlet diameter of the bottom of the base 12, the radius of the inlet fairing 16 having been determined empirically. The following equations use this nomenclature:

Cp = Specific Heat for gaseous media μ = Absolute Viscosity of gaseous media ao = Speed of Sound (Velocity) in gas media

R = Specific Gas Constant for selected gas media

Y = Ratio of Specific Heats g = Acceleration due to Gravity ho = Enthalpy of gas Re = Reynold's Number f = Flow Coefficient mdot = Mass Flow Rate

V = Velocity of gas P = Absolute Pressure

T = Temperature p = Density of gas

M = Mach Number

A = Cross-Sectional Area D = Diameter

Pe = Exit Pressure (Back Pressure) at Aspirator exit k = Drag Loss Factor for Inlet

Afr = Flapper Area Ratio

Alp3 and Alp4 = Mixing Ratios AR = Aspiration Ratio

Floss = Flow Friction Loss

Ln=Length of Nozzle from Throat to Exit For the throat diameter of the Nozzles 30:

ho = Cp»To (2)

2VZb

Tt = (5) γ + 1

Pt pt = (6) R^Tt

mdotn = pt • At • Vt (8)

For the exit diameter of the Nozzles 30:

pt + pe pb = (10) 2

Vt + Ve

Vb = (H) 2 pb»Vb»De

Re = (12) μ

f - 0.3164 (13)

Re 0.25

Pe pe = - (17)

R»Te mdote = pe • Ae • Ve (18)

For the vertical height of the exit plane of the nozzles 30: 1 pratio = (19)

Pa

Po = - (20)

1 + 1.5» Floss •/• pratio • M P-- - pratio • Po (21)

P

P = (23)

R*T mdot = p * <A*V (24)

For the radius of the inlet flairing 16:

Pi pi = (26)

R • Ti mdoti — pi • Vi • Ai (27)

For the throat or smallest inside diameter of the mixing tube 32:

Pm = P + (l-k)»p» — (28)

V_^M*^γ»R*T (30)

mdot

P = (31)

A»V

P=p»R*T (32) For the inside diameter at the top (exit) of the mixing tube: mdotm • lion + mdoti • hi ,„ „. no = (33) mdotn + mdoti

_{T = Λ} ^τ± ₍34₎

|l + _4/_Jp4» O.5« 0' — l)»Af²]

7b = £ (35)

Cp

p = -?— (36)

mdotE = p » A * V (37)

The aspiration ratio is mdotn + mdoti . _ox

AR = (38) mdotn

These equations are put into a computer program and the computer program calculates the aspiration ratio for initial values of the diameters, height, and radius. These initial values are derived from prior art aspirators. The program varies one of the diameters, height, or radius to find the dimension that gives the highest aspiration ratio. After one of the variables has been optimized, one or more of the other variables is manually adjusted and the program is run again with one of the diameters, height, or radius manually selected to be optimized until a high aspiration ratio is achieved. As an alternative embodiment, the program could select each of the diameters, height, and radius in turn and repeat the optimization process. Since changing one of the diameters, height, or radius affects the optimum value for the previous one of the diameters, height, or radius optimized, the program would continue to cycle through each of the diameters, height, and radius variables until a high aspiration ratio is achieved. The current practice is to manually and periodically adjust one of the variables because the program converges for some of the variables but not for others.

There are four constants in the above equations that are derived empirically or calculated from computer simulations. The Flow Friction Loss (Floss) and the Drag Loss Factor for Inlet (k) are numbers calculated by measuring the actual flow rate through an aspirator similar to the present design and comparing the measured rates with the expected rates from equations 20 and 28 without the Floss and k terms, respectively, and adding these constants so that the empirical results match the calculated results. Trie Mixing Ratios Alp3 and Alp4 used in equations 29 and 34, respectively, are losses due to turbulence and cavitation as calculated in a computer simulation of the flow through mixing tube 32.

By the use of these equations an aspirator has been realized that has an aspiration ratio that is significantly higher than the aspiration ratios of prior art aspirators. The embodiments described are chosen to provide an illustration of principles of the invention and its practical application to enable thereby one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore, the foregoing description is to be considered exemplary, rather than limiting, and the true scope of the invention is that described in the following claims.

Claims

CLAIMS:I claim:

1. An aspirator for inflating an aircraft emergency escape slide or life raft comprising: a) a base for receiving a pressurized gas inlet pipe and ambient atmospheric pressure gas; b) a plurality of nozzles having outlets in a plane orthogonal to a gas flow through said base, said nozzles connected to said pressurized gas inlet pipe, and said nozzles positioned inside said base; and c) a mixing tu be attached to said base for receiving the combined pressurized gas and said atmospheric pressure gas, said combined pressurized gas and atmospheric pressure gas having a mass flow more that three times the mass flow of said pressurized gas.

2. The aspirator of claim 1 wherein said base has substantially minimal inlet losses.

3. The aspirator of claim 1 wherein said nozzles have substantially minimal inlet losses.

4. The aspirator of claim 1 wherein said mixing tube has substantially minimal inlet losses.