CN104077436A - Calculation method for energy accumulation of piezoelectric power generation road surface - Google Patents

Abstract

The invention provides a calculation method for energy accumulation of a piezoelectric power generation road surface. An energy output capacity of a power generation road surface for energy accumulation is established by analyzing an electric energy which a piezoelectric element in the power generation road surface can generate under the action of a single standard load and combining with a traffic axle load conversion theory. Various problems caused by mechanical application of the traditional energy output research method in the power generation road surface are avoided based on the power generation energy output analysis method of traffic load accumulation; the calculation method for energy accumulation of the piezoelectric power generation road surface is suitable for electric energy output analytic evaluation of the power generation road surface in different time periods and different road environments.

Description

A kind of piezo-electric generating road surface energy accumulation computing method

Technical field

The invention belongs to road engineering application, relate to piezo-electric generating road surface, be specifically related to a kind of piezo-electric generating road surface energy accumulation computing method.

Background technology

Ended for the end of the year 2013, China's vehicle guaranteeding organic quantity reaches 2.5 hundred million, and wherein automobile pollution reaches 1.27 hundred million, and this is indicating that China formally enters auto age.So huge vehicle guaranteeding organic quantity means that road is by the vehicular load that bears tens times within the scope of China, road vibrates under the repeated action of traffic load, deformation-state variation such as recovery, the Conversion of Energy that traffic load is brought is kinetic energy and strain energy, these energy finally convert heat energy or other energy on road surface to, are dissipated among road environment.According to associated mechanisms, common major urban arterial highway has 15000～20000 the volume of traffic pass through every day, and this is equivalent to every main line every day to 30000～40000 tons of organic energy of little waste.If this part collection of energy is also given and application, exploitation generating road surface not only has academic breakthrough in road engineering, and the economy of Geng Huidui China and society bring beyond measure benefit.

Piezo-electric generating road surface refers to implants bituminous pavement inside or surperficial by the piezoelectric element with Conversion of Energy ability, when automobile travels on road surface, wheel extruding piezoelectric element, microcrystal in its inside makes it produce electric charge, inner when the implanted bituminous sheaths of thousands of piezoelectric elements, under Driving Loading, just can produce huge electric weight.There are some researches show, the automobile 1.6 kilometers of electric weight that can produce 640 kilowatt hours that travel on the bituminous pavement of this implantation energy storage material, can be for the bulb continuous illumination of 1 200 watts 7 days.

At present, the domestic and international research about generating road surface, still in the starting stage, all has no relevant report to the energy output computing method on piezo-electric generating road surface.The existing output of the energy for piezoelectric transducer computing method, conventionally piezoelectric transducer is positioned over the vibration of certain vibration acceleration can be provided, to determine the power source (shaking table) of frequency, go up, by the viscoelasticity differential equation under vibrational state, from point of theory, calculate the electric energy output effect of piezoelectric transducer.If traditional piezoelectric transducer energy output method is applied directly in piezo-electric generating road surface and carries out energy output calculating, compare with real piezo-electric generating road surface duty, there is following problem:

(A) according to moving traffic time distribution character, in time period simultaneously, the number of times that traffic loading passes through, speed are all not identical, load in viscoelastic model is with a certain fixed frequency effect road surface, can not objectively react the duties such as the number of times of Driving Loading and the load action time interval.

(B) in roadnet, Traffic composition is complicated, axle carries to form and complicatedly causes the F (t) in viscoelastic model can not the action effect of good road travel load that is virtually reality like reality to generating road surface.

(C) apply in road surface with piezoelectric element on road, can destroy the continuity of pavement structure, and the Stress damage that causes road surface pavement performance even breaking property destroys, and the elastoplasticity in model is the force-bearing situation of simulated roadway inside completely.

Therefore, traditional piezoelectric elements energy output research method is not suitable for being applied directly to Power Generation Road plane system and carries out electric energy output analysis, if a kind of output of the energy for piezo-electric generating road surface theoretical calculation method can be provided, will the research on generating road surface, application all be had to directive significance.

Summary of the invention

For the piezoelectric energy of traditional piezoelectric elements, export the inapplicable problem that computing method exist in the application of piezo-electric generating road surface, the object of the present invention is to provide a kind of piezo-electric generating road surface energy accumulation computing method, for piezo-electric generating road surface provides a kind of brand-new energy accumulation computing method, avoided energy output research method raw removing in piezo-electric generating road surface of traditional piezoelectric elements to apply mechanically the variety of issue bringing.

In order to realize above-mentioned technical assignment, the present invention adopts following technical scheme to be achieved:

Piezo-electric generating road surface energy accumulation computing method, by (formula 1), calculate:

(formula 1)

Wherein:

N _sfor standard axle load effect number of times,

D ₃₃represent the longitudinal piezoelectric modulus of piezoelectric element;

A represents the area of piezoelectric element;

H represents the thickness of piezoelectric element;

ε _piezothe free dielectric constant that represents piezoelectric element;

L is that piezoelectric element electric energy produces zone length, L=2D+d, and D represents that standard axial conversion is the diameter of equivalent circle after evenly load, d represents that piezoelectric element is along the length of vehicle direct of travel;

p＝0.67MPa；

ν represents the speed that vehicle at the uniform velocity travels.

The present invention is directed to conventional needle and above-mentioned conventional piezoelectric generated energy computing method applied in road surface to the problem existing, propose new piezoelectric energy-conversion output computing method, compared with the existing methods, there is following useful technique effect:

(1) formula comparison that these computing method adopt is simple, does not need to adopt FEM software to carry out Modeling Calculation, and only need carry out simple stress analysis by Small Scale Software BISAR obtains p, obtains the volume of traffic, just can calculate, convenient to use.

(2) avoided conventional energy output research method raw removing in generating road surface to apply mechanically the variety of issue bringing, more effectively consider the chance mechanism of traffic load, overcome the duties such as the number of times of practical engineering application middle rolling car load action and the load action time interval to the impact of calculating.

(3) be applicable to that disalignment is carried, the generating road surface electric energy output under different traffic environment calculates, road surface electric energy output assay can be used for generating electricity in different time sections, different traffic parameter road.

Accompanying drawing explanation

Fig. 1 is that piezoelectric element is subject to the actual forced status under Driving Loading in generating road surface;

Fig. 2 is that piezoelectric element is subject to the equivalent stress under Driving Loading in generating road surface.

In figure, state 1 refers to piezoelectric element in generating road surface and is subject to the initial state of load action; State 2 refers to piezoelectric element in generating road surface and is subject to the end of a period state of load action.

Below in conjunction with drawings and Examples, particular content of the present invention is described in more detail.

Embodiment

It should be noted that the dimension of the physical quantity in the present invention is the standard dimension of each physical quantity in this area, piezoelectric element electric energy produces zone length L and is determined by D and d, the wheel load that D can be BZZ-100 by standard axle load and wheel land pressure and calculate, and d is that the attribute of piezoelectric element itself determines.

Determined after piezoelectricity original paper corresponding parameter piezoelectric coefficient d as longitudinal in piezoelectric element ₃₃, the area A of piezoelectric element, the thickness h of piezoelectricity original paper be, the free dielectric constant ε of piezoelectric element _piezoalso with regard to corresponding, determined.

Defer to technique scheme, following examples provide a kind of piezo-electric generating road surface energy accumulation computing method, and the method is carried out according to following steps:

The pressure that piezoelectric element is subject at vehicle static with while at the uniform velocity travelling, converts the load of wheel in motion according to load stress Equivalent Conversion principle to the effect of stress of piezoelectric element, the equivalent stress that piezoelectric element of the present invention bears on vertical is:

$p=\frac{2\underset{0}{\overset{L}{\∫}}{p}_x}{L}$

In formula: p _xcorresponding stress value on difference within the scope of expression piezoelectric element electric energy generation zone length L;

Traffic load Equivalent Conversion: when criterion of train running axle carry with speed ν pass through road time, piezoelectric element in the stress of bituminous pavement as shown in Figure 1, piezoelectric element is never pressed onto pressurized and is arrived the not process of pressurized again, in this process, the suffered pressure of piezoelectric element is always in variable condition, the electric energy that piezoelectric element produces is also in variable condition, this state is equivalent to local bituminous concrete pavement always under Uniform Load, as shown in Figure 2, and then calculate the energy that piezoelectric element produces.

The stressed Equivalent Conversion of above-mentioned piezoelectric element need to meet following condition:

(1) standard axle load at the uniform velocity passes through road Cross Section with speed ν;

(2) standard axle load is uniformly distributed in two round load equivalent circle scopes;

(3) in generating road surface, in bituminous concrete, segment set material is not considered the concentrated force effect of piezoelectric element, thinks stressed even in piezoelectric element self.

Under Uniform Load, load action diameter of equivalent circle, the wheel load that standard axle load is BZZ-100 is P _mark=25KN, wheel lands pressure p _mark=0.7MPa, has:

Piezoelectric element electric energy of the present invention produces zone length L:

L＝D+d+D

In formula: D represents that standard axial conversion is the diameter of equivalent circle after evenly load, and d represents that piezoelectric element is along the length of vehicle direct of travel;

The traffic load state of ending from piezoelectric element strain original state to strain, the time of walking is:

T＝L/ν

In formula: ν represents the speed that vehicle at the uniform velocity travels;

Standard axle load effect number of times of the present invention converts:

Standard axle load effect times N _sfor: N _s=Σ N _iη _i in formula:

I represents the rank that inhomogeneity profile shaft carries;

η _irepresent that i level axle carries reduction coefficient; N _srepresent standard axle load effect number of times;

N _irepresent that i grade standard axle carries effect number of times;

C ₁expression is by the number of axle coefficient of conversion vehicle, C ₂expression is by the number of axle coefficient of conversion vehicle, P _iexpression is carried by the axles at different levels of conversion vehicle, and P represents standard axle load.

When take design deflection value and brea bed tensile stress at the bottom of layer during as index, axles at different levels carry being calculated as follows shown in table I of equivalent axles Ns that is converted into standard axle load P, and the axle that table I lists some types carries rank, but the axle that is not limited to subordinate's type carries rank.

It should be noted that standard axle load effect times N _sit is the standard volume of traffic, the type of vehicle travelling on road is a lot, the effect that disalignment is carried issues the electrical property that circuit face all shows different variation tendencies, adopt accumulation equivalent axles that inhomogeneity profile shaft is carried and is scaled a certain stationary shaft and carries, the generating road surface electric energy of analyzing under identical load repeatedly under load action goes out output situation.The principle that all kinds of axles carry the employing of effect number of times Equivalent Conversion is for same pavement structure, at all kinds of axles, to carry the damage that issues raw same degree.

Table I: the axle of different stage carries the table of comparisons of the equivalent axles Ns that is converted into standard axle load P

The average voltage U that piezoelectric element under single standard axle load of the present invention effect produces:

When standard axle load is advanced with speed ν, in bituminous concrete, there is less shear stress, and the thickness of the piezoelectric element in bituminous concrete is smaller, shear stress is very little in the polarization that is parallel to piezoelectric element thickness direction, therefore, the generation of piezoelectric element electric energy is mainly from the effect of traffic load compressive stress.

When standard axle load is advanced with speed ν, piezoelectric element is after being subject to directed force F, and the electric charge producing at the thickness direction that is parallel to acting force is:

$Q=\underset{0}{\overset{T}{\∫}}{d}_{33}F$

Under the effect of uniform load, the voltage of piezoelectric element, current constant, therefore the electric current on thickness direction of the piezoelectric element in bituminous concrete is:

$I=\frac{\mathrm{dQ}}{\mathrm{dt}}=\frac{d\left(\underset{0}{\overset{T}{\∫}}{d}_{33}F\right)}{\mathrm{dt}}=d_{33}\mathrm{pA}$

Wherein, piezoelectric element electric capacity is:

$C_{\mathrm{piezo}}=\frac{{\mathrm{\ϵ}}_{\mathrm{piezo}}A}{h}$

The voltage that piezoelectric element thickness direction produces is:

$U=\frac{Q}{{\mathrm{TC}}_{\mathrm{piezo}}}=\frac{\underset{0}{\overset{T}{\∫}}{d}_{33}\mathrm{ph}}{{\mathrm{T\ϵ}}_{\mathrm{piezo}}}=\frac{d_{33}\mathrm{ph}}{{\mathrm{\ϵ}}_{\mathrm{piezo}}}$

In formula: d ₃₃represent the longitudinal piezoelectric modulus of piezoelectric element; A represents the area of piezoelectric element; H represents the thickness of piezoelectric element; ε _piezothe free dielectric constant that represents piezoelectric element;

This piezoelectric element is similar capacitor, also not exclusively the same with capacitor, and it, therefore here should be with Q/T divided by C when calculating the voltage in a certain moment always in transmission of electricity outward _piezo, be exactly according to this charge-averaging once.Because at the uniform velocity, under load action, this electric charge is relatively evenly to produce, and is on average fine.

The energy that piezoelectric element under single standard axle load of the present invention effect produces:

When standard axle load is advanced with speed ν, piezoelectric element is after being subject to load, and at the electric energy that is parallel to the thickness direction of acting force, producing power is P _powerfor:

The energy that in bituminous concrete, piezoelectric element produces under the effect of single standard load is:

To sum up, the cumlative energy that the piezoelectric element under accumulation load produces is:

The wheel carrying according to China test specification acceptance of the bid fiducial axis lands pressure 0.7MPa, calculates piezoelectric element (d ₃₃=256, ε _p=1800) length d is 8cm, thickness h=1mm, area A=40cm ², the equivalent stress p size being subject in the vertical degree of depth of road surface 4cm is 0.67MPa.

Below provide specific embodiments of the invention, it should be noted that the present invention is not limited to following specific embodiment, all equivalents of doing on present techniques scheme basis all fall into protection scope of the present invention.

Embodiment 1: through street

The present embodiment is for certain city expressway, and design parameter is as shown in table 1, provides piezo-electric generating road surface energy accumulation computing method: circular carries out according to following steps:

Table 1 Expressway Traffic parameter

Category of roads	Design rate (km/h)	Represent the speed of a motor vehicle (km/h)	The standard volume of traffic (/d)
				Through street	60～80	70	11300

Step 1, the pressure that in road surface, piezoelectric element is subject at vehicle static with while at the uniform velocity travelling, converts the load of wheel in motion according to load stress Equivalent Conversion principle to the effect of stress of piezoelectric element, and the equivalent stress that piezoelectric element bears on vertical is:

By Small Scale Software BISAR, carrying out simple stress analysis can obtain

In formula: p _xcorresponding stress value on difference within the scope of expression length L;

Traffic load Equivalent Conversion: when criterion of train running axle carry with speed ν pass through road time, the stress of bituminous pavement as shown in Figure 1, piezoelectric element is never pressed onto pressurized and is arrived the not process of pressurized again, in this process, the suffered pressure of piezoelectric element is always in variable condition, the electric energy that piezoelectric element produces is also in variable condition, this state is equivalent to local bituminous concrete pavement always under Uniform Load, as shown in Figure 2, and then calculates the energy that piezoelectric element produces.

The stressed Equivalent Conversion in above-mentioned road surface need to meet following condition:

(1) standard axle load at the uniform velocity passes through road Cross Section with speed ν;

(2) standard axle load is uniformly distributed in two round load equivalent circle scopes;

(3) in generating road surface, in bituminous concrete, segment set material is not considered the concentrated force effect of piezoelectric element, thinks stressed even in piezoelectric element self.

Under Uniform Load, local bituminous concrete length is load action diameter of equivalent circle, and the wheel load that standard axle load is BZZ-100 is P _mark=25KN, wheel lands pressure p _mark=0.7MPa, has:

Step 2, piezoelectric element electric energy produces zone length and is:

L＝D+d+D＝0.506m

The traffic load state of ending from piezoelectric element strain original state to strain, the time of walking is:

T＝L/ν＝0.026s

In formula: ν represents the speed that vehicle at the uniform velocity travels;

Step 3, standard axle load effect number of times converts:

Standard axle load effect times N _sfor: N _s=Σ N _iη _i=11300 times

It should be noted that standard axle load effect times N _sit is the standard volume of traffic, the type of vehicle travelling on road is a lot, the effect that disalignment is carried issues the electrical property that circuit face all shows different variation tendencies, adopt accumulation equivalent axles that inhomogeneity profile shaft is carried and is scaled a certain stationary shaft and carries, the generating road surface electric energy of analyzing under identical load repeatedly under load action goes out output situation.The principle that all kinds of axles carry the employing of effect number of times Equivalent Conversion is for same pavement structure, at all kinds of axles, to carry the damage that issues raw same degree.

Step 4, the average voltage U that the piezoelectric element under the effect of single standard axle load produces:

When standard axle load is advanced with speed ν=70km/h, in bituminous concrete, there is less shear stress, and the thickness of the piezoelectric element in bituminous concrete is smaller, shear stress is very little in the polarization that is parallel to piezoelectric element thickness direction, therefore, the generation of piezoelectric element electric energy is mainly from the effect of traffic load compressive stress.

When standard axle load is advanced with speed U, piezoelectric element is after being subject to directed force F, and the electric charge producing at the thickness direction that is parallel to acting force is:

$Q=\underset{0}{\overset{T}{\∫}}{d}_{33}F=2.65\×{10}^{-9}C$

Under the effect of uniform load, the voltage of piezoelectric element, current constant, therefore the electric current on thickness direction of the piezoelectric element in bituminous concrete is:

$I=\frac{\mathrm{dQ}}{\mathrm{dt}}=\frac{d\left(\underset{0}{\overset{T}{\∫}}{d}_{33}F\right)}{\mathrm{dt}}=d_{33}\mathrm{pA}=0.72\mathrm{\μA}$

Wherein, piezoelectric element electric capacity is:

$C_{\mathrm{piezo}}=\frac{{\mathrm{\ϵ}}_{\mathrm{piezo}}A}{h}=7.2\×{10}^{-9}F$

The voltage that piezoelectric element thickness direction produces is:

$U=\frac{Q}{{\mathrm{TC}}_{\mathrm{piezo}}}=\frac{\underset{0}{\overset{T}{\∫}}{d}_{33}\mathrm{ph}}{{\mathrm{T\ϵ}}_{\mathrm{piezo}}}=\frac{d_{33}\mathrm{ph}}{{\mathrm{\ϵ}}_{\mathrm{piezo}}}=14.2V$

In formula: d ₃₃represent the longitudinal piezoelectric modulus of piezoelectric element; A represents the area of piezoelectric element; H represents the thickness of piezoelectric element; ε _piezothe free dielectric constant that represents piezoelectric element;

Step 5, the energy that the piezoelectric element under the effect of single standard axle load produces:

When standard axle load is advanced with speed ν, piezoelectric element is after being subject to load, and at the electric energy that is parallel to the thickness direction of acting force, producing power is P _powerfor:

The energy that in bituminous concrete, piezoelectric element produces under the effect of single standard load is:

Step 6, the cumlative energy that the piezoelectric element under accumulation load produces is:

Embodiment 2: trunk roads

The present embodiment is for certain city thoroughfare, and design parameter is as shown in table 2, provides piezo-electric generating road surface energy accumulation computing method: concrete calculation procedure is identical with embodiment 1, and result of calculation is E _always=2.04mJ.

Table 2 trunk roads traffic parameter

Category of roads	Design rate (Km/h)	Represent the speed of a motor vehicle (Km/h)	The standard volume of traffic (/d)
				Trunk roads	30～60	45	5000

Embodiment 3: non-parking charge station

The present embodiment is for certain highway non-parking charge station, and design parameter is as shown in table 3, provides piezo-electric generating road surface energy accumulation computing method: concrete calculation procedure is identical with embodiment 1, and result of calculation is E _always=15.6mJ.

Table 3 non-parking charge station traffic parameter

Category of roads	Design rate (Km/h)	Represent the speed of a motor vehicle (Km/h)	The standard volume of traffic (/d)
				Non-parking charge station	20～30	25	21000

Embodiment 4: Car park payment station

The present embodiment is for certain highway Car park payment station, and design parameter is as shown in table 4, provides piezo-electric generating road surface energy accumulation computing method: concrete calculation procedure is identical with embodiment 1, and result of calculation is E _always=33m J.

Table 4 Car park payment station traffic parameter

Category of roads	Design rate (Km/h)	Represent the speed of a motor vehicle (Km/h)	The standard volume of traffic (/d)
				Car park payment station	5～15	10	18000

In different road environments, single piezoelectric element is as shown in table 5 at the electric energy of generation every day, if the electricity collection utilization factor of generating bituminous concrete is 50%, single piezoelectric element producible electric energy every day is 2～33m J.Below fully proved computing method of the present invention can effectively calculate generating road surface energy accumulation.

The energy accumulation result of calculation (mJ) of piezoelectric element in the different road environments of table 5

Claims (1)

1. piezo-electric generating road surface energy accumulation computing method, is characterized in that: by (formula 1), calculate:

(formula 1)

Wherein:

N _sfor standard axle load effect number of times,

D ₃₃represent the longitudinal piezoelectric modulus of piezoelectric element;

A represents the area of piezoelectric element;

H represents the thickness of piezoelectric element;

ε _piezothe free dielectric constant that represents piezoelectric element;

L is that piezoelectric element electric energy produces zone length, L=2D+d, and D represents that standard axial conversion is the diameter of equivalent circle after evenly load, d represents that piezoelectric element is along the length of vehicle direct of travel;

p＝0.67MPa；

ν represents the speed that vehicle at the uniform velocity travels.