Research Article Working Characteristics of Variable ...downloads.hindawi.com/journals/tswj/2014/498934.pdf · Research Article Working Characteristics of Variable Intake Valve in

Research ArticleWorking Characteristics of Variable Intake Valve inCompressed Air Engine

Qihui Yu, Yan Shi, and Maolin Cai

School of Automation Science and Electrical Engineering, Beihang University, Beijing 100191, China

Correspondence should be addressed to Yan Shi; [email protected]

Received 25 July 2014; Revised 28 August 2014; Accepted 31 August 2014; Published 14 October 2014

Academic Editor: Arash Karimipour

Copyright © 2014 Qihui Yu et al.This is an open access article distributed under the Creative Commons Attribution License, whichpermits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

A new camless compressed air engine is proposed, which can make the compressed air energy reasonably distributed. Throughanalysis of the camless compressed air engine, a mathematical model of the working processes was set up. Using the softwareMATLAB/Simulink for simulation, the pressure, temperature, and air mass of the cylinder were obtained. In order to verify theaccuracy of the mathematical model, the experiments were conducted. Moreover, performance analysis was introduced to designcompressed air engine. Results show that, firstly, the simulation results have good consistency with the experimental results.Secondly, under different intake pressures, the highest output power is obtained when the crank speed reaches 500 rpm, whichalso provides the maximum output torque. Finally, higher energy utilization efficiency can be obtained at the lower speed, intakepressure, and valve duration angle. This research can refer to the design of the camless valve of compressed air engine.

1. Introduction

Environmental issues such as fog, haze, greenhouse effect,and acid rains have been widely concerning. Burning of fossilfuels in internal combustion engines (ICE) for transportationis themajor source of environmental issues [1–3]. New energysources such as wind, solar energy, compressed air whichcan replace the fossil fuel are an obvious solution to solveenvironment issues [4]. With respect to environmental pro-tection, the issue of energy expenditure has been emphasized[5]. Some scholars believe traditional automobiles will bereplaced by new energy vehicles in the future. So far, there aresome new energy vehicles, namely, electric vehicles, hybridelectric vehicles, compressed air engines (CAE), and so on.The CAE is the typical product of zero-pollution vehicles,which has been studied bymany scholars and institutions [6].

To ensure smooth running and fast response, the flowof air is controlled by a simple cam mechanism in manyCAE systems [7–9]. Conventional mechanical valve trainsgenerally use valve timings and lifts which are fixed depend-ing upon cam mechanism design. The lack of flexibility ofcamshaft based valve trains to vary timing, duration, and lift

of intake valves is one of the disadvantages [10]. Because theCAE doesmechanical work by expanding compressed air, theflow of compressed air must be controlled to improve energyefficiency. It is obvious that the cammechanism is difficult tomeet the demand. In order to optimize energy efficiency, thevariable intake valve techniques have been used in the CAE[11].

The variable intake valve techniques have the potentialto be widely used in internal combustion engines to reduceenergy losses and fuel consumption [12–17]. Previous studieshave mainly focused on simulations and system integrationsbased on cam mechanism valve. Few studies have beenreported about the variable intake valve investigations inCAE.

This paper focuses on the influences on the perfor-mance of the CAE by the variable intake valve lift andduration. Thus, detailed mathematical models to describethe working process are built and verified by experiments.This paper is organized as follows. In Section 2, detailedmathematical models are discussed. In Section 3, simulationand real experiments results are obtained and compared toverify the accuracy of the theoretical models. In Section 4,

Hindawi Publishing Corporatione Scientific World JournalVolume 2014, Article ID 498934, 9 pageshttp://dx.doi.org/10.1155/2014/498934

2 The Scientific World Journal

the influences on the performance of the CAE by the lift andduration of the variable intake valve are analyzed. Finally,conclusions are presented in Section 5.

2. Theoretical Analysis

To understand the working process of the CAE, we need tostudy the in-cylinder process, which is illustrated in Figure 1.The gas tank provides energy source. The intake pressureis regulated by pressure control unit. Air flow is controlledby solenoid valve. There are mainly three components: thecylinder, the valves, and the tank. In the following, webuild these models based on thermodynamics and pistonkinematics. For a single-stage piston-type CAE, compressedair enters the cylinder through the intake valve and the pistonis pushed by compressed air.Then the intake valve closed aftera specific crank angle, while the compressed air continuesto push the piston down and output work. When the pistonreaches the bottom dead center (BDC), the exhaust valveopens so that the air with residual pressure discharges. Thepiston moves from the BDC to the top dead center (TDC);the CAE completes a work cycle.

2.1. Valve Flow. Because the throttling effect from the intakeor exhaust valve accounts for energy losses, valve flowis critical to the CAE. Valve flow is considered as one-dimensional isentropic flow [18, 19].

If 𝑝𝑑/𝑝𝑢 > 𝑏, the mass flow rate is given by

𝐺 = 𝐴𝑝𝑢√

2𝑘

(𝑘 − 1) 𝑅𝜃𝑢[(

𝑝𝑑

𝑝𝑢)

2/𝑘

− (𝑝𝑑

𝑝𝑢)

(𝑘+1)/𝑘

]. (1)

If 𝑝𝑑/𝑝𝑢 ≤ 𝑏, the flow is choked, and the mass flow rate isgiven by

𝐺 = 𝐴𝑝𝑢√𝑘

𝑅𝜃𝑢(

2

𝑘 + 1)

(𝑘+1)/(𝑘−1)

, (2)

where 𝑏 = (2/𝑘 + 1)𝑘/𝑘−1 is upstream stagnation sound speed.

The valve flow area is represented by 𝐴, which can beexpressed by the following equation:

𝐴 = 𝐶𝑑𝐴V. (3)

The relationship between the valve flow area and the valvelift is defined by the following equation:

𝐴V = 𝑎𝐿V. (4)

The scale factor “𝑎” is defined by

𝑎 =𝐴V𝑚

IVL, (5)

where 𝐴V𝑚 is the maximum valve flow area.

Intake valve Exhaust valve

Pressure control unit

u

𝜃𝜔

Pt Vt Tt

P V T

Figure 1: Cylinder-tank model.

Inta

ke v

alve

lift

(mm

)IVD

IVL

t1 tr t2 t3 tc t4t (s)

Figure 2: Valve lift profile.

We can characterize the camless valve motion by angle(or opening) IVO, maximum lift IVL, and duration IVDof each intake valve. For simplicity, the camless intake andexhaust valve lift profile model is presented by the followingequations:

𝐿V =

{{{{

{{{{

{

𝑠𝑟 (𝑡 − 𝑡1) 𝑡 ≥ 𝑡1, 𝑡 < 𝑡2

IVL 𝑡 ≥ 𝑡2, 𝑡 < 𝑡3

IVL − 𝑠𝑐 (𝑡 − 𝑡3) 𝑡 ≥ 𝑡3, 𝑡 < 𝑡4

0 otherwise,

(6)

where

𝑡1 = 𝑡IVO, 𝑡2 = 𝑡1 + 𝑡𝑟,

𝑡3 = 𝑡2 + 𝑡IVD, 𝑡4 = 𝑡3 + 𝑡𝑐.(7)

The Scientific World Journal 3

𝑠𝑟 and 𝑠𝑐 are fixed in the time domain. A coordinate trans-formation to crank angle domain results in different valveprofiles at different engine speeds. The valve lift profile isshown in Figure 2.

2.2. In-Cylinder Process. The cylinder content is energyexchange process. The pressure and temperature of com-pressed air inside the cylinder are calculated by a globalenergy balance:

𝑑𝑈

𝑑𝑡=

𝑑𝑞

𝑑𝑡+𝑑𝑚𝑖

𝑑𝑡ℎ𝑖 −

𝑑𝑊

𝑑𝑡−𝑑𝑚𝑒

𝑑𝑡ℎ𝑒, (8)

where 𝑑𝑈/𝑑𝑡 is the rate of the internal energy of the air insidethe cylinder, 𝑑𝑞/𝑑𝑡 is the rate of heat transferred from thecylinder wall to the cylinder contents, and 𝑑𝑊/𝑑𝑡 is the rateof work done by the open system (which is equal to 𝑝𝑑𝑉/𝑑𝑡).

The internal energy of the air can be expressed as

𝑑𝑈

𝑑𝑡=

𝑑 (𝑚𝑢)

𝑑𝑡= 𝑚

𝑑𝑢

𝑑𝑡+ 𝑢

𝑑𝑚

𝑑𝑡, (9)

where 𝑢 = 𝐶V𝜃,𝑚 = 𝑚𝑖 − 𝑚𝑒.Substituting (9) into (8) yields

𝑑𝜃

𝑑𝑡=

1

𝑚𝐶V[𝑑𝑞

𝑑𝑡+ ℎ𝑖𝐺𝑖 − ℎ𝑒𝐺𝑒 − 𝑝

𝑑𝑉

𝑑𝑡− 𝑢𝐺] , (10)

where 𝐺𝑖 = 𝑑𝑚𝑖/𝑑𝑡, 𝐺𝑒 = 𝑑𝑚𝑒/𝑑𝑡, 𝐺 = 𝑑𝑚/𝑑𝑡.The rate of the pressure change inside the cylinder is

obtained by the ideal gas law:

𝑝𝑑𝑉

𝑑𝑡+ 𝑉

𝑑𝑝

𝑑𝑡= 𝑚𝑅

𝑑𝜃

𝑑𝑡+ 𝑅𝜃

𝑑𝑚

𝑑𝑡. (11)

2.3. Heat Transfer. In order to evaluate the instantaneous heatinteraction between the cylinder content, the heat transfercoefficient 𝐾𝑤 must be defined. According to literature [20],assuming that the gas velocity is proportional to the averagepiston speed 𝑈𝑝, the heat transfer coefficient 𝐾𝑤 can beexpressed with the following equation:

𝐾𝑤 = (0.1129) 𝑑−0.2

𝑝0.8𝑈0.8

𝑝𝜃−0.594

. (12)

The average piston speed can be expressed by the follow-ing equation:

𝑈𝑝 =𝑆 ⋅ 𝑛

30. (13)

The corresponding heat transfer is

𝑑𝑞

𝑑𝑡= 𝐾𝑤𝐴𝑤 (𝜃𝑤 − 𝜃) , (14)

where the total surface area 𝐴𝑤 can be expressed with crankangle as follows:

𝐴𝑤 (𝜑) =𝜋

2𝐷2+𝜋

2𝐷𝑆

× [1 − cos𝜑 +1

𝜆(1 − √1 − 𝜆2sin2 (𝜑))] .

(15)

Table 1: Initial value of the parameters.

Parameter valueD (m) 0.05S (m) 0.052IVO (deg) 0IVD (deg) 130EVO (deg) 180EVC (deg) 360𝑝𝑠 (bar) 2.5𝑏 0.41𝐶𝑚 2.3𝜆 0.263𝑛 (rpm) 500𝑡𝑟 (s) 0.02𝐶𝑑 0.8

2.4. Piston Ring Friction. The differential element of frictionwork 𝛿𝑊𝑓 for the compression ring can be expressed as

𝛿𝑊𝑓 = 𝜇𝑟𝑝𝜋𝐷𝑑𝑟𝛿𝑆, (16)

where 𝛿𝑆 is piston stroke through which this force acts.This expression is integrated over a complete engine

cycle to account for the work lost to friction, which is thensubtracted from the net cycle work.

3. Simulation and Experimental Validation

3.1. Simulation of the CAE. Theworking characteristics of theCAE are determined by the theoretical analysis mentioned inSection 2. The nonlinear and coupled differential equationsaremodelling inMATLAB/Simulink. Table 1 shows the initialvalues of the parameters.

Figures 3(a), 3(b), and 3(c) show the simulation results.The air pressure of the cylinder is shown in Figure 3(a), theair temperature of the cylinder is plotted against the crankangle in Figure 3(b), and Figure 3(c) depicts the air mass flowof the cylinder curve.

As shown in Figure 3, the pressure, temperature, and themass inside the cylinder of the CAE change periodically.The intake valve opens when the piston reaches the TDC;compressed air from high pressure tank rapidly flows into thecylinder. The pressure inside the cylinder rapidly increasesto the intake pressure. Meanwhile, the mass and temperatureinside the cylinder increase. When the mass flow rate is lessthan the rate of cylinder volume, the pressure of the cylinderdrops dramatically. Meanwhile, the compressed air inside thecylinder expands and leads to the temperature of the cylinderdrop from its peak.

Compressed air no longer flows into the cylinder, whenthe intake valve is closed. At this time, the mass flow of airdrops to zero.The piston is pushed to the BDC depending oncompressed air inside the cylinder expansion. The tempera-ture and pressure inside the cylinder drop dramatically.


1

1.5

2

2.5

Pres

sure

(Pa)

0 180 360 540 720 900 1080Crank angle (deg)

×105

(a)

0 180 360 540 720 900 1080230240250260270280290300310320

Crank angle (deg)

Tem

pera

ture

(K)

(b)

0 180 360 540 720 900 1080

0

1

2

3

Crank angle (deg)

Air

mas

s flow

(kg/

s)

−3

−2

−1

×10−6

(c)

Figure 3: Pressure curve, temperature curve, and mass curve of the cylinder.

The exhaust valve opens when the piston reaches theBDC. The residual compressed inside the cylinder is dis-charged, and the mass inside the cylinder decreases fromits top. Meanwhile, the temperature and pressure inside thecylinder drop to their bottoms.

The above process is repeated and mechanical power canbe output continuously.

According to Figure 3(b), the temperature of the cylinderreaches 240K which may experience icing, so heat exchangemust be used.

3.2. Experimental Verification. The experiments were con-ducted to verify the accuracy of the mathematical model.The experimental apparatus is shown in Figure 4, whichconsists of a high pressure tank, a regulator (IR3020-03BC),a low pressure tank, a throttle valve (AS3001F), two portsolenoid valves, a refit engine with basic parameters shownin Table 2, a data acquisition card (PCI1711) by Advantech,an absolute angular displacement sensor, and program logiccontroller (PLC) by Siemens. In the experiment, a 4-strokegasoline engine was reformed to a compressed air engine bythe intake port and exhaust port solenoid valve. The enginespecifications are shown in Table 2.

In this experiment, firstly, the compressed air sourceworked and the outlet pressure of the regulator was set tothe fixed value. Secondly, the low pressure tank maintainedthe pressure after a period of time, then adjust throttle valvewhich can let compressed air exhausted steadily from the

Table 2: Engine specifications.

Engine model DJ139FMA

Engine type Single cylinder, 4-stroke, spark-ignited,air-cooled engine

Cylinder stroke/bore 50/52mmDisplacement volume 100 cm3

tank. The intake port and the exhaust port solenoid valveswere controlled by PLC with shaft angle which was detectedby absolute value of the angular sensor. The intake portsolenoid valve opened when the piston reached the TDCand closed completely at a crank angle. Then, compressedair inside the cylinder expands. During this process, theexhaust port solenoid stayed closed, and the piston waspushed from the TDC toward the BDC by the incomingcompressed air, producing the power stroke. The exhaustsolenoid valve opened when the piston reaches the BDC.During the process, the intake solenoid valve remainedclosed.The compressed air inside the cylinder was dischargedfrom the cylinder, and the piston moved from the BDCtowards the TDC.The crank angle was measured by absolutevalue of the angular displacement sensor. The last stage wasdata acquisition and storage.

The testing rig is built as shown in Figure 5. The mainparameters of the cylinder are presented in Table 2.


Sensor

PLC

1

2

3

45 6 8

PC

A/D

9

10

11

12

7

𝜑𝜔

(1) Tank(2) Regulator(3) Tank(4) Throttle valve(5) Solenoid valve(6) Air power engine

(7) Pressure sensor(8) Solenoid valve(9) Computer(10) Data acquisition card(11) Angle sensor(12) PLC

Figure 4: Configuration of experimental apparatus.

Figure 5: The experiment of air powered engine.

As shown in Figure 6, the simulation curve trend isconsistent with the experimental curve trend, and the math-ematical model above can be verified. However, there arethree differences between the simulation results and theexperimental results: (1) the maximum pressure is different;(2) the experimental curve is backward offset to simulationcurve; (3) the experiment exhaust pressure value is greaterthan the simulation exhaust pressure value.

The main reasons for the differences are summarized asfollows. Considering the small effective flowing area in theintake solenoid, the throttling effect will be quite evident.Meanwhile, each solenoid valve experiences delay in motion,but the delay time is different under different situation.

In this paper, the simulation is based on the assumptionthat the delay time is constant for simplicity. Therefore, theexperiment pressure curve is backward offset to simulationcurve. And when the exhaust air mass flow is less than therate of cylinder volume, the pressure inside the cylinder willincrease during exhaust process.

Experiment and simulation curves of output torqueare shown in Figure 7. It is obvious that the experimentaland simulation curves have similar trends. Both outputtorque curves decrease when the rotate speed increased. Butthrottling loss is not considered in the simulation process,so the output torque in the simulation is greater than theexperiment value at different crank speeds. It is obvious thatthe differences between experimental and numerical resultsare increased with the crank speed increasing.That is becausethe bearings friction torque, auxiliaries, and gears torquelosses are not considered in the numerical calculated. Thesetorques will increase along with the increase of the crankspeed.

4. Performance Analysis

Energy efficiency evaluation criterion to ICE is not suitablebut not for the CAE. In this section, a new energy efficiencyevaluation, namely, the air power, is briefly introduced toevaluate the energy efficiency of the CAE.

The air power is expressed using the available energy [21],which is expressed as

𝑃 = 𝑝𝑎𝑄𝑎 [ln𝑝𝑠

𝑝𝑎+

𝑘

𝑘 − 1(𝜃𝑠 − 𝜃𝑎

𝜃𝑎− ln

𝜃𝑠

𝜃𝑎)] , (17)

where 𝑄𝑎 is the volume of air at the standard state.The energy efficiency can be expressed by

𝜂 =𝑃

𝑃𝑚, (18)

where

𝑃𝑚 =IT ⋅ 𝑛

9550, (19)

where IT indicates torque.The indicated torque can be expressed by

IT =∫𝑝𝑑𝑉

2𝜋. (20)

From the previous discussion, the performance of CAEcan be obtained in different intake pressure, IVD, and IVL.The initial values of the parameters are shown in Table 1.Intake pressure, IVD, and IVL can be changed for comparisonwhile all the other parameters are kept constant.

Figures 8(a) and 8(b) show the power and torque outputfrom the CAE at various supplied pressures. The highestpower output of 0.3345 kW is obtained at 7 bar and 500 rpm.The highest torque output of 8.4727Nm is obtained at 7 barand 300 rpm. The highest supplied pressure will obtain thehighest torque and power output.


0 180 3601

1.5

2

2.5

Crank angle (deg)

Pres

sure

(Pa)

ExperimentSimulation

×105

(a)

1

1.5

2

2.5

Pres

sure

(Pa)


0 0.2 0.4 0.6 0.8 1 1.2Volume (m 3)

×105

×10−4

(b)

Figure 6: Experimental and simulation curves of cylinder pressure.

250 300 350 400 450 500 550 6001

1.21.41.61.8

22.22.42.62.8

3

Crank speed (rpm)

Out

put t

orqu

e (N·m

)


Figure 7: Experiment and simulation curves of output torque.

The energy efficiencies under various intake pressuresand crank speeds are shown in Figure 8(c). The lowest crankspeed leads to the highest energy efficiency. And the lowestair pressure provides the highest efficiency.

It is clear that increasing supply pressure is beneficial tooutput more power and torque. However, the method willreduce energy efficiency.

Figure 9 shows the performance of the CAE in variousIVD angles at 5 bar intake pressure.

The power and torque output from the CAE are obtainedby simulation at various IVD angles, as shown in Figures 9(a)and 9(b). The highest power output is obtained at 500 rpm inany IVD angle.The output torque increases with the IVD.Theoutput power and torque are equal in different IVD angle at500 rpm. The energy efficiency would decrease with the IVDand can be expressed in Figure 9(c). But when IVD is equalto 20 deg, the efficiency will drop at crank speed of 100 rpm.That is because the more the compressed air enters into CAEat the lowest crank speed, the higher the pressure exhaustsare.

Figure 10 shows the performance of the CAE in variousIVL at 5 bar intake pressure.

The power and torque output from the CAE are obtainedby simulation at various IVL, as shown in Figures 10(a) and10(b). The output power increases with the crank speed. Butwhen crank speed is lower than 400 rpm, the output powerhas little change at various IVD. That is because in low crankspeed the air flow mass is almost stable with different IVL.Meanwhile, at the beginning, the output torque increaseswith the increase of the crank speed and reaches its peaks atdifferent crank speeds and IVL. The energy efficiency woulddecrease with the crank speed and large IVL is beneficialto improve the energy efficiency which can be expressedin Figure 10(c). Throttling effect will decrease in largeIVL.

5. Conclusions

In this paper, the mathematical model was built. Simulationand experimental studies on the CAE were done, and theconclusions are summarized as follows.

(1) Compressed air pressure inside the cylinder andoutput torque have the same changing tendency inboth simulation curve and experimental curve.

(2) The highest power output is obtained at 500 rpm,and the highest torque output is obtained at 300 rpmat different intake pressures and different IVDangles.

(3) When crank speed is higher than 200 rpm, higherenergy utilization efficiency can be obtained at thelower speed, intake pressure, and IVD.

(4) The output torque increases with the increase ofthe crank speed and reaches its peaks at differentcrank speeds and IVL. And large IVL is beneficial toimprove the energy efficiency.


100 150 200 250 300 350 400 450 500 550 6000

0.050.1

0.150.2

0.250.3

0.35

Crank speed (r/min)

Out

put p

ower

(kW

)

7bar

2bar

(a)

100 150 200 250 300 350 400 450 500 550 600Crank speed (r/min)

0123456789 7bar

2bar

Out

put t

orqu

e (N·m

)

(b)

100 150 200 250 300 350 400 450 500 550 600Crank speed (r/min)

0.10.20.30.40.50.60.70.80.9

Effici

ency 7bar

2bar

(c)

Figure 8: The relationship of intake pressure and performance of CAE.

0

0.05

0.1

0.15

0.2

0.25

Out

put p

ower

(kW

)

100 150 200 250 300 350 400 450 500 550 600Crank speed (r/min)

50deg

20deg

(a)

22.5

33.5

44.5

55.5

6

100 150 200 250 300 350 400 450 500 550 600Crank speed (r/min)

50deg

20deg

Out

put t

orqu

e (N·m

)

(b)

0.20.25

0.30.35

0.40.45

0.50.55

0.60.65

0.7

Effici

ency

100 150 200 250 300 350 400 450 500 550 600Crank speed (r/min)

50deg

20deg

(c)

Figure 9: The relationship of IVD and performance of CAE.


2mm

5mm

100 200 300 400 500 600Crank speed (r/min)

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4O

utpu

t pow

er (k

W)

(a)

2mm

5mm

100 200 300 400 500 600Crank speed (r/min)

4.5

5

5.5

6

Out

put t

orqu

e (N·m

)

(b)

2mm

5mm

100 200 300 400 500 600Crank speed (r/min)

0.5

0.55

0.6

0.65

0.7

Effici

ency

(c)

Figure 10: The relationship of IVL and performance of CAE.

Nomenclature

𝐴: Area (m2)𝑏: Critical pressure ratio𝐶V: Specific heat at constant volume (J/(kg⋅K))𝐶𝑝: Specific heat at constant pressure

(J/(kg⋅K))𝐶𝑑: The valve discharge coefficient𝐷: Piston diameter (m)𝐸: Thermodynamic internal energy (J)𝐺: Air mass flow (kg/s)ℎ: The enthalpies of air (W/(m2K))IVO: Valve lift opening angle (∘CA)IVL: Valve maximum lift (m)IVD: Valve duration angle (∘CA)𝐾𝑤: Heat transfer coefficient𝑘: Specific heat ratio𝐿: Valve lift (m)𝑚: Air mass (kg)𝑛: Engine speed (rpm)𝑝: Pressure (Pa)

𝑞: Heat exchange (J)𝑄: The volume of air (m3/s)𝑅: Gas constant (J/(kg⋅K))𝑆: Piston stroke (m)𝑠𝑟: Intake valve opening inclination𝑠𝑐: Intake valve closing inclination𝑡: Time (s)𝑡𝑟: The time for intake valve to reach maxi-

mum lift (s)𝑡𝑠: The time for intake valve from maximum

lift to closing (s)𝑈: The internal energy of the air (J)𝑢: Velocity (m/s)𝑉: Volume (m3)𝑊: Energy (J)𝜑: Crank angle (rad)𝜇𝑟: The sliding friction coefficient𝜂: Efficiency𝜔: Crank speed (rad/s)𝜃: Temperature (K).


Subscripts

𝑎: Atmosphere𝑑: Downstream side𝑖: Entering𝑒: LeavingIVO: Redundant use of openingIVD: Duration of intake valve opening𝑜: Valve𝑠: Supply of CAE𝑡: Tank𝑢: Upstream sideV: Valve.

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper.

References

[1] H. Chen, Y. Ding, Y. Li, X. Zhang, and C. Tan, “Air fuelled zeroemission road transportation: a comparative study,” AppliedEnergy, vol. 88, no. 1, pp. 337–342, 2011.

[2] B. R. Singh and O. Singh, “A study of performance output ofa multivane air engine applying optimal injection and vaneangles,” International Journal of Rotating Machinery, vol. 2012,Article ID 578745, 10 pages, 2012.

[3] T. N. Veziroglu and S. Sahin, “21st Century’s energy: hydrogenenergy system,”EnergyConversion andManagement, vol. 49, no.7, pp. 1820–1831, 2008.

[4] K. Morita, “Automotive power source in 21st century,” JSAEReview, vol. 24, no. 1, pp. 3–7, 2003.

[5] K. T. Chau and Y. S.Wong, “Overview of powermanagement inhybrid electric vehicles,” Energy Conversion and Management,vol. 43, no. 15, pp. 1953–1968, 2002.

[6] C. A. Ordonez, “Liquid nitrogen fueled, closed Brayton cyclecryogenic heat engine,” Energy Conversion and Management,vol. 41, no. 4, pp. 331–341, 2000.

[7] C.-Y. Huang, C.-K. Hu, C.-J. Yu, and C.-K. Sung, “Experimentalinvestigation on the performance of a compressed-air drivenpiston engine,” Energies, vol. 6, no. 3, pp. 1731–1745, 2013.

[8] A. N. Da, T. Jian, and C.-J. Zuo, “Designing and experimentofa compressed-air engine,” Journal of Heifei University ofTechnology, vol. 28, no. 6, pp. 612–615, 2005.

[9] S. Trajkovic, P. Tunestal, and B. Johansson, “Investigation ofdifferent valve geometries and valve timing strategies and theireffect on regenerative efficiency for a pneumatic hybrid withvariable valve actuation,” SAE International, 2008.

[10] S. A. G.M. Saied, S. A. Jazayeri, and A. H. Shamekhi, “Modelingof variable intake valve timing in SI engine,” inProceedings of theSpring Technical Conference of the ASME Internal CombustionEngine Division (ICES ’06), pp. 789–803, May 2006.

[11] M. H. Christopher and D. Lee, “Block: compressed air engine,”U.S. Patent 8667787, 2014.

[12] R. Kumar and A. K. Dixit, “Combustion and emission char-acteristics of variable compression ignition engine fueled withJatropha curcas ethyl ester blends at different compression ratio,”Journal of Renewable Energy, vol. 2014, Article ID 872923, 12pages, 2014.

[13] M. Izadi Najafabadi and N. Abdul Aziz, “Homogeneous chargecompression ignition combustion: challenges and proposedsolutions,” Journal of Combustion, vol. 2013, Article ID 783789,14 pages, 2013.

[14] E. Sher and T. Bar-Kohany, “Optimization of variable valve tim-ing for maximizing performance of an unthrottled SI engine-atheoretical study,” Energy, vol. 27, no. 8, pp. 757–775, 2002.

[15] M. Golcu, Y. Sekmen, P. Erduranli, andM. S. Salman, “Artificialneural-network based modeling of variable valve-timing in aspark-ignition engine,” Applied Energy, vol. 81, no. 2, pp. 187–197, 2005.

[16] G. Fontana and E. Galloni, “Variable valve timing for fuel econ-omy improvement in a small spark-ignition engine,” AppliedEnergy, vol. 86, no. 1, pp. 96–105, 2009.

[17] A.-F. M. Mahrous, A. Potrzebowski, M. L. Wyszynski, H. M.Xu, A. Tsolakis, and P. Luszcz, “A modelling study into theeffects of variable valve timing on the gas exchange process andperformance of a 4-valve DI homogeneous charge compressionignition (HCCI) engine,” Energy Conversion and Management,vol. 50, no. 2, pp. 393–398, 2009.

[18] Y. Shi and M. Cai, “Working characteristics of two kinds of air-driven boosters,” Energy Conversion and Management, vol. 52,no. 12, pp. 3399–3407, 2011.

[19] X. Wang, T.-C. Tsao, C. Tai, H. Kang, and P. N. Blumberg,“Modeling of compressed air hybrid operation for a heavy dutydiesel engine,” in Proceedings of the Spring Technical Conferenceof the ASME Internal Combustion Engine Division, pp. 173–186,April 2008.

[20] U. Bossel, “Thermodynamic analysis of compressed air vehiclepropulsion,” Journal of KONES, Internal Combustion Engines,vol. 12, pp. 3–4, 2005.

[21] M. Cai, K. Kawashima, and T. Kagawa, “Power assessment offlowing compressed air,” Journal of Fluids Engineering, Transac-tions of the ASME, vol. 128, no. 2, pp. 402–405, 2006.

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