Design and characteristic research of double-acting aircraft deicing fluid pump*

Miao GONG, Zhi-wei XING, Li-wen WANG

1Department of Aeronautical Automation, Civil Aviation University of China, Tianjin 300300, China;2Aviation Ground Special Equipment Research Base, CAAC, Tianjin 300300, China

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Design and characteristic research of double-acting aircraft deicing fluid pump*

Miao GONG? 1,2, Zhi-wei XING1,2, Li-wen WANG1,2

1Department of Aeronautical Automation, Civil Aviation University of China, Tianjin 300300, China;2Aviation Ground Special Equipment Research Base, CAAC, Tianjin 300300, China

Abstract:Filling speed of deicing fluid is an important factor that affects the efficiency of airport deicing operation. In this paper, we design a double-acting large flow reciprocating pump for aircraft deicing equipment. We demonstrate the principle, the design drawing and the design calculation of key components. The pressure-flow characteristics of double-acting pump are analyzed through modeling and simulation methods; the optimal program of system damping and flow output are obtained by the simulation experiment of changing piston clearance. We implement a practical experimental analysis, which is based on the optimal parameters obtained from the simulation, to test the rationality of the simulation experiment. The result is shown that, according to the viscosity of the deicing fluid, the system damping, flow and pulsation are optimal relevance and the flow steady output when the piston clearance is 3mm. This verifies the rationality and feasibility of the design. Within the operating pressure range of the pump, the output flow and ripple suppression achieve the desired effect, and the performance is better than the existing similar deicing equipments. This design provides a reference for the related equipment design and industrial applications.

Key words:Double-acting pump, AMESIM, Piston clearance, Pressure-flow characteristic, Deicer equipment

1.Introduction

In the process of aircraft deicing operation, filling speed of deicing fluid is the principal element, which directly affects the efficiency of deicing operations. Currently, several major north airports have built a kind of large deicing fluid filling system that consist of a stationary fluid filling and ratable matching station and mobile high flow fluid filling station[1]. In deicing fluid filling system, the efficiency of the whole system is directly affected by the speed of filling pumps. The system need several large flow pumps working together, and the physical characteristics of deicing fluid require that the pumps would not generate shear force to deicing fluid during the operation because it can cause some loss of fluid viscosity. Furthermore, using bottom filling hole for filling the large mobile deicing fluid station requires the pumps having definite pressure resistance. Moreover, the filling pump is expected to lower the pulsation of outputting flow to enhance the real time mixing ratio accuracy of deicing fluid and water. The lower output pulsation can also reduce the resonance between the mobile fluid filling station and the pipeline to keep stability of system[2].

To achieve these requirements, we designed a large flow and high performance double-acting deicing fluid filling pump. Through modeling and simulation, we verified the feasibility of design and analyzed the performance parameter of the pump, and then we found out the optimal configuration among damping clearance and output ripple, which was tested by experiment. This paper can provide the basis for high-performance deicer equipment design and manufacturing.

2.Design principles of double-acting aircraft’s deicing fluid pump

2.1.Design goals

The main component of the deicing fluid is propylene glycol or ethylene glycol, together with a small amount of anti-corrosion agents, antifoam agents, antioxidants, flame retardants, stabilizers and the like[3]. The fluid can be achieved with a different freezing point and refractive index by mixing different proportions of water. It’s required filling to deicing vehicles or mobile fluid stations rapidly. According to above requirements, the design goals are stated as follows：

① The pump should not produce shear stress on the fluid molecules in the filling process which affects the physical and chemical characteristics of deicing fluid;

② Pump cavity is made of stainless steel;

③ Maximum flow of pump>30 m3/h;

④ Maximum bear pressure>0.5 MPa.

2.2.Design principles

According to these requirements, we designed a double-acting piston-type deicing fluid pump. The cavity is made of 304 stainless steel. The structure principle diagram is shown as Figure 1.

Figure 1.Double-acting deicing fluid pump structure principle diagram

Two same built plunger pump cylinders(3) are linked by a crank connecting rod (1) via piston(2), the fluid inlet pipeline (4) connects with fluid inlet check valve(5) on each plunger pump cylinder, the fluid drain pipeline (6) connects with drain check valve(7) on each plunger pump cylinder. The plunger pump cylinder is divided into two zones (A and B). Each zone has two check valves. Considering the corrosion caused by the deicing fluid, the plunger pump cylinder (3), the fluid inlet pipeline (4) and the fluid drain pipeline (6) is made of stainless steel materials.

The working process is introduced as follows. First, start the power source (after turning on the power), crank link mechanism drive two cylinder pistons reaching the limit position of the right side (dashed line) then move to the left, the piston moves to the left so that the deicing fluid in zone A is pushed, meanwhile, the inlet check valve of zone A is closed and the drain check value of zone A is opened, the pressure pushes the fluid out of the drain check. At the moment the cylinders in zone B become vacuum, the pressure of the inlet pipeline is greater than the cylinders inside, pushing the fluid through inlet check valve into zone B, meanwhile, the drain check valve in zone B is closed. When the pistons reaches the limit position of the left side (dashed line) then move to the right, the working principle is exactly the same. When the drain check valve of both zones is opened, the deicing fluid will be pushed out quickly at a certain pressure. Crank link mechanism drives the piston for reciprocating linear motion in this way. The processes of suction and drainage are continuous. The two cylinders at left and right sides suck up and drain deicing fluid twice respectively in a working cycle. This working form can effectively ensure the continuity and stability of filling.

3.Design and calculations of key components

3.1.Power conversion

The maximum working pressure:

p=0.5 MPa=0.5×106N/m2

Volume flow (single cylinder flow):

Q0=20 m3/h=20×0.000 277 m3/s

Pressure unit dimension：L-1MT-2

volume flow unit dimension：L3T-1

Power unit dimension：L2MT-3

Calculation according to the dimension as follows:

(L-1MT-2)×(L3T-1)=L2MT-3

The result of the calculation above is same as the power unit dimension, so the effective power output for unilateral pump is:

P1=p·Q=2.777 kW

The effective power output for bilateral pump is:

P2=2P1=5.554 kW

When the motor output power is 11 kW and the output flow remains the same, the instantaneous maximum output pressure can be up to 1MPa[4].

3.2.Calculations of the transmission ratio

We set piston diameter asD, the piston radius asR, the schedule of length asL, the pump flow asQ, the reciprocating frequency of the pump asf. Then we choose double-acting plunger pump piston diameterD=150 mm, the linear motion of the piston strokeL=120 mm, motor speedn=1 400 r/min. The calculation is as follows.

The design volume flow (unilateral pump flow):

Q0=20 m3/h which can be converted to 0.333 3 m3/min

The flow of a double-acting plunger pump piston once reciprocating is:

Q1=2πR·2L=0.075×0.075×3.1415×0.12×2=0.004 24 m3

So the flow of a double-acting plunger pump piston once reciprocatingQ1is 0.004 24 m3.

The pump reciprocating frequency of one minute is:

f=Q0÷Q1=0.333 3÷0.004 24=78.6

The transmission ratio between the motor and the pistons is:

i=n/f=1 400÷78.6=17.81

3.3.Design calculations of key parts

The static bearing capacity under rated pressure and flow is known that the rated pressure is 0.5 MPa and unilateral pump design flow is 20 m3/h. We set the axial force in piston cylinder asF, the radius of the bolt asR1, the piston rod radius asR2, the tensile strength as t, the crank pin radius asR3.

We choose bolt radiusR1=9 mm, the piston rod radiusR2=12 mm, crank pin radiusR3=15 mm.

Maximum axial force of piston in cylinder is:

F=0.075×0.075×3.141 5×0.5×1 000 000=8 835.729 N

Maximum piston cylinder axial force is approximately equal to 883.572 9 kg.

We choose the materials of the piston rod and bolts are both of 304stainless steel, which has 150 MPa tensile strength; the material of crank pin is 40Cr which has 800 MPa tensile strength and 500 MPa shearing strength. The axial tensile strengthFin piston cylinder is decided by cylinder head tightens bolts cross-sectional area and the piston rod minimal cross section. The verifying calculation is as follows:

The maximum tension of a single bolt (total four) can withstand is:

F0=R12×π×t

So:F0=0.009×0.009×π×150×1 000 000=38 170 N

The maximum tension of the bolt group is:

F1= 4F0=152 680 N

The maximum tension of the bolt rod is:

F2=R22×π×t

That is:F2=0.012×0.012×π×150×1 000 000=67 858 N

The maximum shear-force of turn pin:

F3=R32×π×t

So：F3=0.015×0.015×π×500×1 000 000=353 429 N

It is known thatF1,F2,F3are all greater than the maximum axial bearing capacity of the cylinderF. Therefore, axial tensile forceFin the piston cylinder which is 8 835.729 N is under safe limits, even if the axial force in the movement increases seven times.

The power transmission is designed by a belt speed shift and a gear speed shift. Then it drives the eccentric sheave to rotate. The power transmits through crank pin of the eccentric sheave, then transfer to piston rod for reciprocating motion. The first stage belt speed shift is consisted of a large belt wheel on axle-1 and a small belt wheel on motor. Diameter of small wheel is designed to be 100 mm, and 410 mm for the diameter of large wheel. So the first transmission ratio is 4.1. The second gear shift stage is consisted of a small gear on axle-1 and a large gear on axle-2. Teeth number of small one is designed as 18, and 74 for big wheel, so the second transmission ratio is also 4.1.

The two stage gear ratio is first stage ratio multiplied by the second ratio which is 16.81. Motor speed is 1 400 r/min, the transmission ratio is 16.81, the reciprocating piston frequencyf1=83.28,f1>f. Therefore, the output flow will be greater than the theoretical side 20 m3/h, the bilateral will be greater than 40 m3/h.

3.4.General layout scheme of double-acting deicing fluid pump

We demonstrate the general layout scheme of double-acting deicing fluid pump base on the above design and calculations, as shown in Figure 2.

Figure 2.General layout scheme of double-acting deicing fluid pump

4.Modeling and simulation

4.1.Model construction

The deicing operation requires that the double-acting deicing fluid pump can output huge flow in specific pressure range. At present, typeⅠaircraft deicing fluid is frequency-used which is mainly consistedofpropylene glycol. Its viscosity coefficient is higher so the output flow of reciprocating pump will produce larger pulsation. We adopted the software AMESIM[5] to simulate and model, so that we can validate the feasibility of the design and find out the best configuration of high performance case, then we can analyze the optimum parameters of damping clearance for reducing the flow ripple on the premise of guaranteeing rated flow. AMESIM is based on the concept of “basic element”, that is, extract the smallest unit of engineering system from all models which allows the user to describe the function of all systems and components in the model without writing any program codes, it allows users liberate from the tedious mathematical modeling to focus on the design of the physical system[6-7].

Figure 3 is AMESIM simulation model of double-acting deicing fluid pump. The speed after reducing is included in the motor simulation data; crank linkage corresponds to the actual eccentric wheel mechanism. The initial phase of two cylinders and the phase difference can be set in the parameter setting; block of hydraulic cylinder, ball valve and combination of weight modules correspond to the reciprocating pump cylinder; safety valve corresponds to the actual safety valve; throttle valve corresponds to the actual ball valve. During the simulation, 12 different size diameter of the ball valve were input as batch parameters; by changing the piston clearance to find the optimum damping solution.

As shown in Figure 3，the two modules in upper left corner of the figure are used to set the physical parameters and the inertial parameters of the medium.

Figure 3.AMESIM simulation model of double-acting deicing fluid pump

4.2.Settings of model parameters

The main parameters of the model are shown in Table 1 which is according to the design plan.

Table 1.The main parameters of the system

The ambient temperature of model is 20℃, the atmosphere is standard, typeⅠaircraft deicing fluid is the simulation fluid whose main component is propylene glycol. The main parameters of fluid are shown in Table 2.

Table 2.Fluid physical parameters

Throttle valve internal structure was simulated with SolidWorks. We calculate the area under different angles respectively, and calculate the equivalent diameter according to the cross-sectional area. The calculation process is shown in Figure 4, and the equivalent diameter of sectional area is shown in Table 3.

Figure 4.Calculation process of valve opening area

Opening/(°)Cross-sectionalarea/mm2Equivalentdiameter/mm07853.98100.0106695.1792.3205605.1984.5304417.2175.0403251.3764.3502157.9052.4551656.9646.0601196.2139.065785.2131.670434.8223.575161.3814.3802.751.9

4.3.Simulation

We start the simulation according to the parameters settings of the system model building and simulation running and the selection of sub models. After the simulation operation, we can calculate the average flow rate and average pressure value in front of ball valve by the post-processing function of AMESIM[8].Considering the pipe friction, we set pipeline model as compressible friction model. When the simulation medium is typeⅠdeicing fluid and the piston clearance is 0.5 mm, the system average flow curve and average pressure curve are shown respectively as Figure 5 and Figure 6.

Figure 5.The average flow curve

Figure 6.The average pressure curve

According to the simulation results, we obtain the relation curve of the average flow and the average pressure, as shown in Figure 7.

Figure 7.The average pressure-flow curve

The results is shown that the output flow peak of the double-acting pump within the scope of 0.000 43 to 0.290 4 MPa is 44 m3/h after running stability, and it is greater than the maximum flow of design, inside leakage in the pump is smaller. When the pressure is between 0.290 4 to 0.679 9 MPa, the flow has a slow decrease trend. The flow is still 35 m3/h or more, when the pressure below 0.679 9 MPa, the pump shows good performance parameters. The output flow and continuity is superior to traditional single-acting reciprocating pump.

In order to further optimize output flow pulsation of system, considering the larger viscosity properties of deicing fluid, we adjust the piston clearance from 0.5 mm to 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm and 3 mm respectively, then we do modeling and simulation respectively, analyze the damping effect of the piston clearance[9-10] changes on the system. Considering the maximum working pressure of mobile fluid station charging is about 0.041 5 MPa (this typical data comes from deicing Fluid Filling System of BCIA), the six condition of valve opening is most close to the actual operation. We intercept the flow simulation curve of pump from 45 to 50 seconds, at this time it has run into stable output, as shown in Figure 8.

Figure 8.The flow curve under different piston clearance

The curve indicates that with the gradual increase of piston clearance, the system average flow, average pressure and flow fluctuations are slow downward. Simulation measures that the system damping and flow parameters achieved in a relative optimal configuration when the piston clearance is 3 mm. By system calculations, the output flow pulsation is reduced to 0.198 6 m3/h, it’s better than the other 5 piston clearance conditions.

We capture the average pressure-flow curve point at 3 mm piston clearance, as shown in Figure 9. Due to high viscosity of deicing fluid, the flow can still reach 31.42 m3/h when the pressure value is 0.532 MPa, the performance of pump still exceed the design requirements. Under this condition, although the output flow reduces some, it can still meet the design flow. The pulsation decreased and the output showed better continuity; the resonance between pipe system and mobile deicing fluid station can be reduced effectively, the decrease of pulsation may promote more accurate of real-time mixing ratio for deicing fluid and water.

Figure 9.The average flow-pressure curve of 3 mm piston clearance condition

5.Experiment

According to the simulation results, the actual piston clearance is made for 3 mm to test, as shown in Figure 10. Pressure sensor is installed in the pipeline behind throttle valve and flow sensor is installed in export pipeline. The pressure and flow data of difference process in system is collected and transmitted into computer through AD board. We calculate the average value of each point after removing interference data. Then we obtain the pressure-flow curve as shown in Figure 11 and the output flow curve of typical work condition as shown in Figure 12.

It is shown in the experiment that the pressure-flow curve tendency of experiment is coincident with the simulation. Contrasting with Figure 7 and Figure 9, owing to some inevitable internal leakage in actual working condition, the experiment flow is lower than the simulation. When the pressure ranges from 0.017 7 MPa to 0.023 4 MPa, the internal leakage is mainly caused by the retaining valves of suction. When the pressure is above 0.023 4 MPa, the mechanical seal of retaining valve is enhanced along with the accretion of pressure, it cause the flow curve rising, the flow is at peak of 36.1 m3/h when the pressure is 0.042 4 MPa, under this condition, system leakage is at the fewest point. Considering the normal working pressure of actual filling system is about 0.041 5 MPa (BCIA data), the flow of pump is desirable. According to the performance of pump, it can meet the expected value for actual working well.

Figure 10.Photo of experiment

Figure 11.The average flow-pressure curve of experiment

Figure 12.The average flow curve under 0.424 MPa condition of experiment

According to the simulation, we choose the pressure condition of 0.042 4 MPa to analyze the output flow pulsation of system. As shown in Figure 12, the average flow curve of experiment is under the condition of type Ⅰ deicing dynamic viscosity, 3 mm piston clearance. By calculations of computer, we obtain that the output flow pulsation is within 0.231 2 m3/h and the output flow has good continuity.The result testified the experimental validity of simulation and showed that the increase of piston clearance has a damping effect on output flow. According to the experiment, the maximum flow can reach 36.1 m3/h, which is 1.8 times than the same level reciprocating pump from market. It is shown that the double-acting pump has good performance parameter, can meet the demand of high flow and stable filling for large mobile deicing fluid station.

6.Conclusion

1) In order to enhance the efficiency of aircraft deicing operation, we designed a double-acting large flow reciprocating pump which is aimed at aircraft deicing fluid viscosity characteristics and requirements of deicing operations. We demonstrated the detailed design calculation and the overall design drawing.

2) By AMESIM modeling and simulation, we analyzed the pressure-flow characteristics of the pump, it is shown that the pump performance parameters can meet the design expectation and commendably satisfy the requirements of deicing operation. The simulation results testified the reasonability of design.

3) By the simulation experiment of changing the clearance of the piston, it is shown that on the premise of guaranteeing output flow, the increase of piston clearance can eliminate flow pulsation to some extent. We implemented the practical experiment based on the optimum parameters of the piston clearance from the simulation experiment. The result is shown that according to typeⅠdeicing fluid, when the piston clearance is 3 mm, the system damping, flow and pulsation are optimal relevance, flow steady output. It verified the rationality and feasibility of the design.

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鹽霧試驗對電子設備機箱涂層的影響

鞠成玉?，王曉慧， 朱潤， 任曉明

北京航空航天大學 可靠性與系統(tǒng)工程學院，北京100191

雙作用式飛機除冰液泵設計及特性研究*

龔淼? 1,2，邢志偉1,2，王立文1,2

1中國民航大學 自動化學院，天津300300；2中國民航航空地面特種設備研究基地，天津300300

摘要：除冰液的加注速度是影響機場除冰作業(yè)效率的重要因素。設計了一種面向飛機除冰裝備領域的雙作用式大流量往復泵，給出了設計原理、主要部件設計計算書及總體設計圖。通過建模仿真分析雙作用泵的壓力流量特性；通過改變活塞間隙的仿真實驗得到系統(tǒng)阻尼和流量輸出的折中優(yōu)化方案，并依據(jù)仿真得到的最佳參數(shù)進行實驗，驗證仿真分析的合理性。結果表明：根據(jù)除冰液的粘度，活塞間隙在3 mm條件下，系統(tǒng)阻尼、流量、脈動到達最優(yōu)關聯(lián)，流量輸出平穩(wěn)，驗證了設計方案的合理性和可行性。泵在工況壓力范圍內(nèi)，輸出流量和脈動抑制均達到預期效果，性能超越現(xiàn)有同類除冰加液設備性能，為行業(yè)應用和相關設備的設計提供參考。 飛機服役于沿海環(huán)境中，各部位極易受到鹽霧等腐蝕性氣氛的影響。通過鹽霧試驗對機載電子設備機箱涂層進行耐蝕性檢測，利用掃面電鏡、電化學工作站，紅外光譜等方法對涂層進行分析，研究其在鹽霧條件下的失效機理及退化規(guī)律。結果表明：涂層在鹽霧環(huán)境下的失效主要是由于物理過程，而非化學老化導致，且涂層失效過程主要包含3個進程，用交流阻抗譜對其整個腐蝕過程可以精確地表征。

關鍵詞：雙作用泵；AMESIM；活塞間隙；流量壓力特性；除冰設備 復合涂層； 鹽霧試驗； 交流阻抗

中圖分類號：TH112 TH86

DOI:10.3969/j.issn.1001-3881.2014.06.010

Received: 2013-10-06

*Project supported by the Joint Funds of the Natural Science Foundation of China and Civil Aviation Administration of China (Grant No.60939001) and National Key Technology Research and Development Program of China (Grant No.2012BAG04B02)

? Miao GONG. E-mail:mgong@cauc.edu.cn