CN104809260A - Design method of high-efficient thruster with coaxial and reverse dual propellers - Google Patents

Abstract

The invention discloses a design method of a high-efficient thruster with coaxial and reverse dual propellers. The design method comprises the steps: firstly, establishing whole flow velocity, flow rate and energy math equations according to principles that motion laws of air stream in the front and rear propellers are respectively independent and inter-related in the aerofoil theory; secondly, determining an inflow angle, an outflow angle and a mounting angle of each aerofoil of dual propellers according to the above math equations; thirdly, calculating total energy and axial energy, determining internal diameters, external diameters and specific values of two propellers; finally, designing and manufacturing a propeller model according to the above parameters, and performing experimental verification and parameter amendment; the coaxial and reverse dual propellers manufactured by utilizing the design method are capable of remarkably promoting thrusting ability and power-energy conversion efficiency.

Description

The method for designing of coaxial reverse double-helix oar high efficiency propeller

Technical field

The present invention relates to a kind of coaxial angle of rake method for designing of reverse double-helix oar, relate to a kind of method for designing of coaxial reverse double-helix oar high efficiency propeller (the plug-in oar of the yacht side of a ship) with active diversion, rectification function.

Background technology

Yacht outboard thruster common is at present mostly single screw, and it is actually one does not have shell, does not have the axial flow pump of water conservancy diversion leaf and rectification leaf yet, and by the impact of various interference factor, its propulsive efficiency is not high.Standard axial flow pump generally comprises three parts: 1, with the suction chamber of water conservancy diversion leaf; 2, the blade wheel chamber of switching energy; 3, with the delivery chamber of rectification leaf.The flowing of fluid in impeller is very complicated spatial movement.Under hypothesis fluid is the condition of incompressible one dimensional flow, the velocity triangle of the inflow point of propeller blade profile (intercepting on certain Radius periphery) can be drawn, as shown in Figure 1,

U ₁, u ₂be respectively as fluid is in the peripheral speed (convected velocity) at import and export place,

Cause same rotating speed and the constant u of u value with Radius ₁=u ₂=u;

V ₁, v ₂for import and export place fluid-phase is to the absolute velocity of pump, because hypothesis fluid is incompressible one dimensional flow v _{1 α}=v _{2 α}.V _{1 α}, v _{2 α}for v ₁, v ₂axial component.

ω ₁, ω ₂for import and export fluid-phase is for the relative velocity of blade profile, in like manner, ω _{1 α}=ω _{2 α};

ω _{1 α}, ω _{2 α}for ω ₁and ω ₂axial component, ω _{1 α}, ω _{2 α}also v is equaled _{1 α}=v _{2 α}.Can the velocity triangle of import and export be drawn in together thus, as shown in Figure 2;

Get ω ₁and ω ₂geometrical mean ω _∞for relative velocity during unlimited multiple-blade,

The following vector correlation and mathematical formulae can be drawn thus:

$\stackrel{\‾}{u}+\stackrel{\‾}{\mathrm{\ω}}=\stackrel{\‾}{v}---(2-1);$

u ₁＝u ₂＝u （2-2）；

v _1α＝v _2α＝ω _1α＝ω _2α＝ω _∞α（2-3）；

${\mathrm{\ω}}_{\∞}=\sqrt{{\mathrm{\ω}}_{\mathrm{\α}}^2+{\left(\frac{{\mathrm{\ω}}_{1\mathrm{\α}}+{\mathrm{\ω}}_{2\mathrm{\α}}}{2}\right)}^2}=\sqrt{v_{\mathrm{\α}}^2+(u-{\left(\frac{v_{1u}+v_{2u}}{2}\right)}^2)}---(2-4);$

$\mathrm{tg}{\mathrm{\β}}_{\∞}=\frac{{\mathrm{\ω}}_{\mathrm{\α}}}{{\mathrm{\ω}}_{\∞u}}=\frac{2{\mathrm{\ω}}_{\mathrm{\α}}}{{\mathrm{\ω}}_{1u}+{\mathrm{\ω}}_{2u}}=\frac{v_{\mathrm{\α}}}{u-\frac{v_{1u}+v_{2u}}{2}}---(2-5);$

Energy equation according to wing theory is derived:

$\begin{array}{cc}{P}_T=C_L\frac{l}{t}\frac{u}{v_{\mathrm{\α}}}\mathrm{\ρ}\frac{{\mathrm{\ω}}_{\∞}^2}{2}\frac{\sin ({\mathrm{\β}}_{\mathrm{\ω}}+\mathrm{\λ})}{\cos \mathrm{\λ}}& \left(\mathrm{Pa}\right)---(2-6);\end{array}$

In formula, symbol is shown in Fig. 3,

F _lfor fluid is to the lift of the leaf wing;

F _dfor fluid is to the resistance of the leaf wing;

L is that the wing side of a ship is long;

T is pitch;

ρ is fluid density;

C _lfor lift coefficient;

λ is angle between lift and drag vector;

Cos λ ≈ 1, the sin(β when λ angle is very little _∞+ α) ≈ sin β _∞;

P _tcan be reduced to:

$\begin{array}{cc}{P}_T=C_L\frac{l}{t}u\frac{\mathrm{\ρ}{\mathrm{\ω}}_{\∞}}{2}& \left(\mathrm{Pa}\right)---(2-7);\end{array}$

This formula represents: the energy of (r+dr) in blade a certain r radius circumference aspect, gross energy should be P _tto impeller radius from r ₁to r ₂integration:

$\mathrm{\Σ}{P}_T={\∫}_{r_2}^{r_1}{P}_T\mathrm{dr};$

Above formula is based upon on hypothesis basis that is desirable, that simplify.The actual motion boundary condition of single screw does not observe theoretical setting, wherein the most obvious difference be ships and light boats when moving ahead, before ships and light boats stern screw propeller, produce negative pressure, fluid forms irregular whirlpool.Before the wing, being one by the fluid of airfoil theory setting has the hypothesis of the parallel-flow of the angle of attack not exist.It is not consistent with line direction before ships and light boats that fluid promotes produced energy by blade.This weakens the propulsive efficiency of blade greatly.So, do not have a greatly reduced quality with single screw energy conversion efficiency compared with axial flow pump of rectification leaf (room) with water conservancy diversion leaf (room).

Have coaxial reverse double-helix oar thruster product to occur in the recent period, its main starting point based on:

1, from axial flow pump energy equation, P _twith u and be directly proportional.Rotating speed one timing, along with the increase of radius r, u and all increase, because the energy on different radii stream interface is different, the energy on large r stream interface will be sacrificed for maintenance homenergic, and total energy is reduced, adopt twin screw to replace the single-blade that the bodily form is larger, process homenergic problem can be suffered a loss less;

2, P _tcertain r stream interface increases with rotating speed and increases, improving rotating speed can remarkable lifting fluid energy conversion ability, for promoting the propelling power of engine capacity and blade in the cabin that yacht is narrow and small, best measure promotes engine and angle of rake rotating speed, engine (thruster) rotating speed of middle-size and small-size yacht is within the scope of 4000 ~ 8000rpm, and single-blade leaf is not suitable with high rotating speed;

3, Ye You producer notices the irregular of fluid before single screw, and adopts the twin screw with diversion function, but the summary of just experiment experience, do not rise to theoretical level, do not possess extensive directive significance.

Summary of the invention

In order to make up above deficiency, the invention provides a kind of method for designing of coaxial reverse double-helix oar high efficiency propeller, the coaxial reverse double-helix oar thruster propulsion capability adopting this method for designing to manufacture and propulsive efficiency high, the high dynamic property requirement of yacht can be met.

The present invention in order to the technical scheme solving its technical matters and adopt is: a kind of method for designing of coaxial reverse double-helix oar high efficiency propeller, and described method for designing comprises the following steps:

Step one: first according to fluid in wing theory in the characteristics of motion of front and back screw propeller and the respective independent principle interrelated again, set up overall flowing velocity, flow, energy mathematical equation:

${\mathrm{\ω}}_{\∞}=\sqrt{{\mathrm{\ω}}_{\∞1}^2+{\mathrm{\ω}}_{\∞2}^2-2{\mathrm{\ω}}_{\∞1}{\mathrm{\ω}}_{\∞2}\cos ({\mathrm{\β}}_{\∞1}+{\mathrm{\β}}_{\∞2})}$

$\mathrm{tg}{\mathrm{\β}}_{\∞}=\frac{{\mathrm{\ω}}_{\∞1\mathrm{\α}}+{\mathrm{\ω}}_{\∞2\mathrm{\α}}}{{\mathrm{\ω}}_{\∞1u}-{\mathrm{\ω}}_{\∞2u}}$

$P_T=C_L\frac{l}{t}u\frac{\mathrm{\ρ}\sqrt{{\mathrm{\ω}}_{\∞1}^2+{\mathrm{\ω}}_{\∞2}^2-2{\mathrm{\ω}}_{\∞1}{\mathrm{\ω}}_{\∞2}\cos ({\mathrm{\β}}_{\∞1}+{\mathrm{\β}}_{\∞2})}}{2}$

Wherein: ω _∞for relatively twin-propeller relative velocity;

β _∞for ω _∞with the angle of circumferential alignment;

P _tfor twin-propeller gross energy;

Step 2: the ω of screw propeller when different fluid inlet angle, efflux angle before and after setting up _{∞ 1}, ω _{∞ 2}, β _{∞ 1}, β _{∞ 2}, ω _∞and β _∞mAP, according to the above-mentioned MAP determination twin screw fluid inlet angle of the leaf wing, efflux angle and established angle separately;

Step 3: calculate gross energy P _twith axial energy P _{t α}, and then determine the internal diameter r of blade ₁with external diameter r ₂and value;

Step 4: manufacture and design Rotor Blade Model;

Step 5: carry out model test in flume test device, checking is amendment design parameter also, completes impeller design.

As a further improvement on the present invention, described step 3 is calculated by computer software.

As a further improvement on the present invention, described step 4 utilizes fluid kinematic similitude three law and 3D printing technique to manufacture and design Rotor Blade Model.

As a further improvement on the present invention, the water in described step 5 in tank is dynamical state.

Technique effect of the present invention is: the present invention is according to the characteristics of motion separately independent principle that again interrelate of fluid in wing theory at front and back screw propeller, set up overall flowing velocity, flow, energy mathematical equation, then determine the twin screw fluid inlet angle of the leaf wing, efflux angle and established angle calculate gross energy P separately _twith axial energy P _{t α}, and then determine the internal diameter r of blade ₁with external diameter r ₂and value; According to above-mentioned calculating, coaxial reverse double-helix oar model is manufactured and designed, the model precession mode draft experiment manufactured and designed carries out checking and amendment design parameter, the coaxial reverse double-helix oar of the design's method gained has significant performance advantage compared with single screw, adopts the produced coaxial reverse double-helix oar of the design's method to significantly improve propelling power and the energy conversion efficiency of outboard screw propeller.

Accompanying drawing explanation

Fig. 1 is the fluid velocity triangle that blade profile is imported and exported;

Fig. 2 is the overlap of aerofoil profile import and discharge velocity triangle;

Fig. 3 is the acting force in aerofoil profile;

Fig. 4 is twin screw relative velocity figure;

Fig. 5 is twin screw relative velocity triangle;

Fig. 6 is the performance curve of axial flow pump;

Fig. 7 is coaxial two-direction propeller arrangement figure;

Fig. 8 is for making dynamic tank test unit.

embodiment

Embodiment: a kind of method for designing of coaxial reverse double-helix oar high efficiency propeller, concrete steps are as follows:

Step one: the movement velocity of fluid in twin screw and the foundation of energy spectrometer and mathematical formulae:

According to the simplification energy equation that wing theory is derived be from formula, the parameter of relation fluid energy size is very complicated to be implicative of each other again, L, t, u, ω _∞all relevant variable, and u and ω _∞relation is had, in order to study the kinematic relation of fluid between two propellers, if C again with the velocity triangle of blade rotating speed n, radius r and import and export _l, L, t, u, ρ be fixed number, namely the structure of blade is determined, only research ω on a certain radius liquid stream interface under certain rotating speed _{∞ 1}and ω _{∞ 2}relation, namely two impellers import and export velocity triangle (flowing to angle and efflux angle) relation, to establish total energy equation, seek the maximization of fluid energy and the lifting of propulsive efficiency.

The leaf grating that a certain radius r liquid stream interface has been shaped is drawn, as shown in Figure 4;

Follow wing theory separately according to each blade of the characteristics of motion of coaxial antiport twin screw propulsion system fluid and draw twin-propeller relative velocity triangle, as shown in Figure 5;

The leg-of-mutton ω of twin screw relative velocity _∞relative velocity common in two screw propellers can be regarded as, α _∞for ω _∞with the angle of axis, β _∞for ω _∞with the angle of circumferential alignment.

From relative velocity triangle:

${\mathrm{\ω}}_{\∞}=\sqrt{{\mathrm{\ω}}_{\∞1}^2+{\mathrm{\ω}}_{\∞2}^2-2{\mathrm{\ω}}_{\∞1}{\mathrm{\ω}}_{\∞2}\cos ({\mathrm{\β}}_{\∞1}+{\mathrm{\β}}_{\∞2})}---(3-1);$

$\mathrm{tg}{\mathrm{\β}}_{\∞}=\frac{{\mathrm{\ω}}_{\∞1\mathrm{\α}}+{\mathrm{\ω}}_{\∞2\mathrm{\α}}}{{\mathrm{\ω}}_{\∞1u}-{\mathrm{\ω}}_{\∞2u}}---(3-2);$

Formula (3-1) is substituted into formula (2-7) to obtain:

$P_T=C_L\frac{l}{t}u\frac{\mathrm{\ρ}\sqrt{{\mathrm{\ω}}_{\∞1}^2+{\mathrm{\ω}}_{\∞2}^2-2{\mathrm{\ω}}_{\∞1}{\mathrm{\ω}}_{\∞2}\cos ({\mathrm{\β}}_{\∞1}+{\mathrm{\β}}_{\∞2})}}{2}---(3-3);$

P _tbe equivalent to the pressure that fluid gives impeller, its axial thrust load is only the expulsive force for ships and light boats.

That is:

Step 2: the ω of screw propeller when different fluid inlet angle, efflux angle before and after setting up _{∞ 1}, ω _{∞ 2}, β _{∞ 1}, β _{∞ 2}, ω _∞and β _∞mAP, according to the above-mentioned MAP determination twin screw fluid inlet angle of the leaf wing, efflux angle and established angle separately, specific as follows:

Due to the formula of formula in step one (3-4) amount very complicated and changeable, mathematical operation is very difficult.But as can be seen from formula: work as β _{∞ 1}+ β _{∞ 2}after > 90 °, along with two jiaos and increase propelling power also increase, β _{∞ 1}+ β _{∞ 2}maximal value is reached, β when=180 ° _∞increase and also have same effect, at the ω at certain rotating speed n and diameter of propeller blade place _{∞ 1}, ω _{∞ 2}, β _{∞ 1}, β _{∞ 2}main transformer factor Deng variable is the fluid inlet angle of Ye Yi, efflux angle and established angle.Because the speed of incoming flow direction of screw propeller 1 is difficult to determine, come under the flow path direction prerequisite consistent with line direction before ships and light boats in hypothesis, screw propeller energy conversion efficiency will lower than actual calculated value.Necessary sacrifice will be made for this reason; But efflux angle can control.One of core of the design is exactly the best fluid inlet angle of the efflux angle determination screw propeller 2 by screw propeller 1.Screw propeller 1 plays water conservancy diversion.The determination of the efflux angle of screw propeller 2 will ensure the maximization of axial energy, and screw propeller 2 plays rectified action simultaneously.The through transport of leading of two screw propellers has been moved the water conservancy diversion of a typical axial flow pump, has been driven the course of work of stream, rectification, can significantly improve angle of rake propulsive efficiency.One of feature of the present invention is establishment P _{t α}calculating and operational software, ω can be calculated rapidly after the fluid inlet angle providing blade and efflux angle _∞, ω _{∞ α}, P _{t α}value, and set up ω _∞and ω _{∞ α}mAP;

Step 3: calculate gross energy P _twith axial energy P _{t α}, and then determine the internal diameter r of blade ₁with external diameter r ₂and value, specific as follows:

P _{t α}represent the axial thrust of a certain fluid aspect, increase along with the increasing of impeller radius r.The change of different aspects flow velocity must cause the Radial Flow between leaf grating, produces flow losses.For reducing flow losses, during designing airfoil, its established angle β _yspan L and pitch t will change with r.Propulsion capability and flow efficiency produce contradiction, value has a great impact the energy conversion ability of blade and efficiency.When other condition is identical less, ability and efficiency higher.Twin screw has obvious superiority than single screw;

Step 4: manufacture and design Rotor Blade Model:

(1) Rotor Blade Model is designed:

1. according to the output power P of engine when rated speed _ewith rotating speed n, deduction gearing efficiency, determines angle of rake shaft power.Because outboard thruster is made up of 4 pairs of spiral bevel gears, diesis universal joint, the mechanical efficiency of power train is lower, therefore gets η _m=0.9 ~ 0.92.

2. divide engine shaft power equivalent equally screw propeller 1 and screw propeller 2, then:

$P_{\mathrm{ch}}=\frac{1}{2}{P}_e{\mathrm{\η}}_m=(0.45~0.46)P_e;$

3. the flow q when rated speed is gone out according to the axial flow pump flow of Fig. 3-3 and the performance curve preresearch estimates of shaft power _v,

4. rule of thumb preliminary election number of blade and blade mean radius r ₀;

generally get number of blade Z=3;

5. according to the r carrying out hypothesis that flow path direction is parallel to pump shaft and determine screw propeller 1 ₀the fluid inlet angle of place's leaf wing, ω when calculating and provide multiple efflux angle (established angle is determined) thereupon _{∞ 1}, β _{∞ 1}mAP.

6. number of blade Z and the mean radius r of screw propeller 2 is got ₀identical with screw propeller 1, the efflux angle of opposed helical oar 1, determines one group of best fluid inlet angle and 2 ~ 3 efflux angles (rectified action of efflux angle requires that its angle changes at about 90o).Calculate and provide ω _{∞ 2}, β _{∞ 2}mAP.Match from MAP with formula (3-1) and find out ω _∞and β _∞maximal value, determine the efflux angle of screw propeller 1 and fluid inlet angle, the efflux angle of screw propeller 2 thus, and both established angles.

7. last according to homenergic require and determine r ₁, r ₂value, and L, t, the β on different radii _y.

8. reverse checking computations get the rationality of parameter.

9. manufacture model propeller by similarity theory and 3D printing technique, in tank simulation test, verifying result of design, and through repeatedly revising, reaching desired design target.

(2) propulsion capability and energy conversion efficiency analysis:

Propulsion capability and energy conversion efficiency are two different concepts, separately analyze.

1. propulsion capability analysis:

Propulsion capability can represent with the flow velocity of fluid between screw propeller leaf grating and flow, and flow is large, the high then propulsion capability of flow velocity is large.

q _vT＝v _αA＝ω _αA；

Q _vTfor theoretical delivery (m ³/ s)

V _α=ω _αfor the axial component (m/s) of absolute velocity v and relative velocity ω

A is effective area of passage (m of axial flow pump ²)

After the inflow of blade, efflux angle are determined, q _vTand v _α=ω _αonly relevant with rotating speed n, leaf wing radius r.A and r ₂-r ₁size relevant.N improves v and strengthens, v _α=ω _αand q _vTincrease.A is with r ₂-r ₁increase and strengthen.R ₂increasing is limited to physical strength and flow losses, under the condition that physical strength allows, reduces radius r ₂and r ₂-r ₁value, improving rotating speed n is then the most effective measures increasing propulsion capability.Twin screw is conducive to the lifting of propulsion capability.

2. energy conversion efficiency analysis:

This analysis is the difference in the single screw and twin screw energy conversion efficiency with equal propulsion capability.If the energy conversion efficiency of single screw is η, η=η _mη _vη _hdue to value is large, lacks the rectification after the water conservancy diversion before blade and blade, and its flow losses are large, flow efficiency η _hlow, generally between 0.75 ~ 0.85.

η ₁＝η _mη _vη _h＝0.65～0.78；

η _mfor mechanical efficiency single screw, 2 couples of conical gear η _m=0.94 ~ 0.95;

η _vfor volumetric efficiency generally gets η _v=0.95 ~ 0.96;

η _hfor flow efficiency generally gets η _h=0.75 ~ 0.85;

The conversion efficiency with its screw propeller 1 of twin screw system of water conservancy diversion rectification function is basic similar to single screw, because of be worth little, flow efficiency is slightly higher.Screw propeller 2 is that conversion efficiency is apparently higher than single screw at a more satisfactory operation.Test shows: twin-propeller energy conversion efficiency is similar to available following formula and expresses: higher than single screw 5 ~ 10 percentage points.

(3) manufacture Rotor Blade Model: according to fluid kinematic similitude three law designing and calculating, and print manufacture coaxial two-direction Design of Propeller model through 3D, as shown in Figure 7;

Step 5: carry out model test in test unit in tank, checking is amendment design parameter also, completes impeller design, specific as follows:

First dynamic tank test unit is manufactured and designed, as shown in Figure 8;

The coaxial two-direction Design of Propeller model and single screw model model that adopt method for designing manufacture of the present invention are not put into dynamic tank experimental provision and carries out simulated experiment, comparison of test results is as follows:

Claims (4)

1. a method for designing for coaxial reverse double-helix oar high efficiency propeller, is characterized in that: described method for designing comprises the following steps:

Step one: first according to the characteristics of motion separately independent principle that again interrelate of fluid in wing theory at front and back screw propeller, set up overall flowing velocity, flow, energy mathematical equation:

${\mathrm{\ω}}_{\∞}=\sqrt{{\mathrm{\ω}}_{\∞1}^2+{\mathrm{\ω}}_{\∞2}^2-2{\mathrm{\ω}}_{\∞1}{\mathrm{\ω}}_{\∞2}\cos ({\mathrm{\β}}_{\∞1}+{\mathrm{\β}}_{\∞2})}$

$\mathrm{tg}{\mathrm{\β}}_{\∞}=\frac{{\mathrm{\ω}}_{\∞1\mathrm{\α}}+{\mathrm{\ω}}_{\∞2\mathrm{\α}}}{{\mathrm{\ω}}_{\∞1u}-{\mathrm{\ω}}_{\∞2u}}$

$P_T=C_L\frac{l}{t}u\frac{\mathrm{\ρ}\sqrt{{\mathrm{\ω}}_{\∞1}^2+{\mathrm{\ω}}_{\∞2}^2-2{\mathrm{\ω}}_{\∞1}{\mathrm{\ω}}_{\∞2}\cos ({\mathrm{\β}}_{\∞1}+{\mathrm{\β}}_{\∞2})}}{2}$

Wherein: ω _∞for relatively twin-propeller relative velocity;

β _∞for ω _∞with the angle of circumferential alignment;

P _tfor twin-propeller gross energy;

Step 2: the ω of screw propeller when different fluid inlet angle, efflux angle before and after setting up _{∞ 1}, ω _{∞ 2}, β _{∞ 1}, β _{∞ 2}, ω _∞and β _∞mAP, according to the above-mentioned MAP determination twin screw fluid inlet angle of the leaf wing, efflux angle and established angle separately;

Step 3: calculate gross energy P _twith axial energy P _{t α}, and then determine the internal diameter r of blade ₁with external diameter r ₂and value;

Step 4: manufacture and design Rotor Blade Model;

Step 5: carry out model test in flume test device, checking is amendment design parameter also, completes impeller design.

2. the method for designing of coaxial reverse double-helix oar high efficiency propeller according to claim 1, is characterized in that: described step 3 is calculated by computer software.

3. the method for designing of coaxial reverse double-helix oar high efficiency propeller according to claim 1, is characterized in that: described step 4 utilizes fluid kinematic similitude three law and 3D printing technique to manufacture and design Rotor Blade Model.

4. the method for designing of coaxial reverse double-helix oar high efficiency propeller according to claim 1, is characterized in that: the water in described step 5 in tank is dynamical state.