performance, combustion and emission ...

Vijaya Kumar K.R. et. al. / International Journal of Engineering Science and Technology Vol. 2(7), 2010, 2876-2885

PERFORMANCE, COMBUSTION AND EMISSION CHARACTERISTICS OF PZT LOADED CYANATE MODIFIED EPOXY COATED COMBUSTION CHAMBER IN DIESEL ENGINE VIJAYA KUMAR K.R* Department of Mechanical Engineering,, College of Engineering Guindy, Anna University, Chennai, India. [email protected]

SUNDARESWARAN V Professor, Department of Mechanical Engineering,, College of Engineering Guindy, Anna University, Chennai, India. [email protected] Abstract : Energy conservation and emissions have become increasing concern over the past few decades. PZT loaded cyanate modified epoxy (60EPCY 20PI) coated material were initially investigated for adiabatic diesel engines based on first law of thermodynamics prediction of significant fuel economy improvements, reduction in heat rejection and potential increased power density of the diesel engines. The purpose of 60EPCY 20PI is to focus on developing binder systems with low thermal conductivity and improve the coating durability under high load condition. The coating material is made up of 20% Lead Zirconate Titanate (PZT) in 60% Cyanate modified Epoxy system. The triazine ring of cyanate ester offers better thermal resistance characteristics to the epoxy system. Experimental investigation is carried out under different load condition on a single cylinder diesel engine with PZT loaded cyanate modified epoxy resin system of 0.5 mm thickness to the piston, cylinder head with valves and cylinder liner. The result showed 15.89 %of reduced specific fuel consumption. Emissions of unburnt hydrocarbon, carbon monoxide are reduced. Keywords: Diesel engine, Emissions, Thermal resistance 1. Introduction Diesel engine has become the most fuel efficient power plant sustainable for mobile application. It has assumed a leading role in both transport and agricultural sector because of its outstanding fuel economy and its lower running cost. Even in diesel engine the coolant and exhaust gases carry substantial amount of fuel energy away from the combustion chamber [Tamilporai (2004)].By using PZT loaded cyanate modified epoxy system (60EPCY 20PI) coated combustion chamber there is reduction in heat transfer to the coolant and an improvement in power output along with an increase in exhaust energy. The transfer of heat is conducted through the combustion chamber elements,like valves, piston surfaces and liners. Ceramic of these element by a composite with low thermal conductivity keeps the heat in the chamber and hence increases the temperature [Venkatesh (1973), Prasad (1990), Hejwowski (2002)]. The requirement for more efficient engines in the future will also require even higher operating temperatures. Ceramic with their high temperature resistance, may offer an excellent coating surface to reduce the amount of degradation and to extend the life. Composite coating absorbs thermal shocks and protect the substrate. The primary purposes of high temperature structural coatings are to enable high temperature components to opertate at even high temperature, to improve component durability of engines [Cengiz Oner (2009)]. 60EPCY 20PI are characterized by excellent mechanical and low thermal conductivity properties, high chemical and corrosion resistance, low shrinkage on curing and the ability to be processed under a variety of conditions.

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Vijaya Kumar K.R. et. al. / International Journal of Engineering Science and Technology Vol. 2(7), 2010, 2876-2885 In this paper main emphasis is placed on investigating the effect of 60EPCY 20PI coated combustion chamber on the engine fuel consumption and thermal efficiency. Emission measurement of unburnt hydrocarbon, carbon monoxide and NOx were also conducted. 2. 60EPCY 20PI Material Epoxy resin LY556 (diglycidyl ether of bis phenol A), curing agent HT972 (DDM - diamino diphenyl methane), Arocy b10 (bis phenol dicyanate), E-glass fibre and lead zirconate titanate (PZT). The composites are fabricated from E-glass fiber and commercial epoxy resin/cyanate modified epoxy resin. The glass fiber with an aerial density of 200 g/m2 was used as the reinforcement for composite laminate. The liquid epoxy was taken in a beaker, which was heated to 90oC to lower the resin viscosity and desired amount of cyanate was added into resin. The Cyanate loading is 60% and 20% PZT loading by weight of epoxy resin. The mixture was degassed in a vacuum oven followed by addition of DDM (curing agent) in 27% by weight of epoxy and stirred for 3 minutes at 90oC. It is coated on the combustion chamber which has high temperature phases like tetragonal and cubic structures. The mechanical properties are investigated by using universal Testing Machine (Model H50K-S, Hounsfield Test Equipment Ltd, UK).The cross head speed was 1mm / min The span length of the specimen was 150mm .Tensile modulus studies were evaluated as per ASTM D 3039.The flexural strength and flexural modulus of the composites were studied as per ASTM – D790. The crosshead speed was 1.0 mm / min. The double cantilever beam (DCB) test samples for GIC fracture toughness measurements were prepared according to the ASTM D 5528 (dimension 125 x 25 x 3mm) with a preinitiated crack of 50mm. Aluminium hinges were attached to the surfaces of the specimens to facilitate crack propagation. Measurements of load and crack displacement were taken at the initial crack propagation, at 1mm intervals for first 5mm, then at 5 mm interval up to a total crack length of 45 mm and at 1mm intervals for the last 5 mm giving a total of 19 readings. Three methods of data reduction were applied, using software programs, the data quoted being those obtained by compliance method at peak load [9]. The displacement of crack was observed using a camera and the test was carried out in universal testing machine [5].Major headings should be typeset in boldface with the first letter of important words capitalized. Table 1 shows the mechanical properties of 60EPCY 20PI. Table 1. Mechanical Properties of 60EPCY 20PI

Properties Tensile Stength (MPa) Tensile Modulus (GPa) Flexural Strength (MPa) Flexural Modulus (GPa) Fracture Toughness (kJ/m2s) Damping Factor Stiffness (N/mm)

60EPCY 20PI 355 7.98 465 9.5 1.6 0.10029 62.97

3. Test Engine Tests were carried out on a kirloskar, single cylinder, water cooled, direct injection, four stroke stationary diesel engine. Once the steady state condition was reached after loading then the readings such as time taken for 10cc fuel consumption, exhaust gas temperature, HC, CO and NOx were taken. The air flow rate was measured by a U tube manometer. The pollutant emissions such as unburnt hydrocarbon, carbon monoxide, carbon dioxide, oxides of nitrogen and oxygen concentrations were measured by AVL 444 exhaust gas analyzer. The analyzer consists of an electrochemical sensor, which converts the concentration of different species in the exhaust gas into corresponding electrical signals. The exhaust gas temperature was measured by using a k- type thermocouple.

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Fig. 1. Photographic view of 60EPCY 20PI coated piston, cylinder head with valves and liner

Fig. 2. Photographic view of Experimental set-up Table 2. Technical specification of the engine used in the experiments

Engine Type Bore Diameter Stroke Length Brake Power Compression Ratio Speed Injection Type Cooling Fuel Injection No.of.Cylinder Injection Pressure

Kirloskar, Vertical, Four stroke diesel engine 80mm 110mm 3.68kW 16:1 1500rpm Direct Injection Water 23o bTDC 1 210 bar

3. Diesel Cycle Simulation In this simulation during the start of compression, the mole of different species that are considered to be present, includes oxygen, nitrogen from intake air and CO2 ,water (gaseous), nitrogen and oxygen from the residual gases. The overall complete combustion equation considered as

m m m   m  Cn H m    n  O2  3.773 * N 2   nCO2    * H 2O  3.773  n   * N 2  (  1) n  O2 4 4 4   2 

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Vijaya Kumar K.R. et. al. / International Journal of Engineering Science and Technology Vol. 2(7), 2010, 2876-2885 λ Represents the excess air factor n Number of carbon atoms in diesel m Number of hydrogen atoms in diesel Volume at any crank angle is calculated from this equation

 B 2 S  V  VC    * * 1  z  z 2  sin 2  4 2  





1 2

  cos   

(2)

where

z 

lc s   2

(3)

Vc = Cylinder volume (m3) B = Bore diameter (m) S = Stroke length (m) lc = Connecting rod length (m) z = Constant Initial Temperature and Pressure During Start of Compression R

 V  Cv (T1 ) T2  T1 *  1   V2 

(4)

V  T  P2   1  *  2  * P1  V2   T1 

(5)

T1 = Temperature of previous crank angle (K) T2 = Temperature of crank angle (K) P1 = Pressure of previous crank angle (N/m2) P2 = Pressure of crank angle (N/m2) V1 = Volume of previous crank angle (m3/kg) V2 = Volume of crank angle (m3/kg) Work done in each crank angle

P P  dW   1 2 (V2  V1 )  2 

(6)

The unburned zone temperature is calculated using the equation

 pu   p   soi 

T u  T soi 

 1 

(7)

Tu = Unburned zone Temperature (K) Tsoi = Temperature during start of ignition (K)

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Vijaya Kumar K.R. et. al. / International Journal of Engineering Science and Technology Vol. 2(7), 2010, 2876-2885 Pu = Unburnt pressure (N/m2) Psoi = Pressure during start of ignition (N/m2) Annand’s Convective Heat Transfer Model The gas-wall heat transfer is found out using ANNAND’S convective heat transfer model. Radiation heat transfer is also estimated in this model

dQ Re b  ak (TC  TW )  c(TC4  TW4 ) dt d

(8)

Thermal conductivity is calculated for each change in viscosity

k

C p  prod

(9)

0.7

Viscosity of the combustion gases are calculated from

 prod  

 air (1  0.027 )

= Fuel Air equivalence ratio Viscosity of air at each temperature change is calculated from

 air  3.3 *10 7 (T1 ) 0.7

(9)

T1 Temperature of previous crank angle Reynolds number for each time step is calculated as the viscosity varies

Re 

dV p  prod

(10)

where Vp = Mean piston speed (m/s)

V

p

 2* N * S     60 

(11)

N = Speed (rpm) S = Stroke length (m) Cylinder mean temperature is calculated from

T u T g   T c  2   

(12)

Tu = Unburned zone temperature (K) Tg = Temperature of burned zone at the crank angle (K) a = 0.49; b = 0.7; c =1.6x10-12. Wall Heat Transfer Model This model is used to find out conductive heat transfer through cylinder to the coolant and thereby to find instantaneous wall temperature

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 Q   w Tw  Tg    2 l   h g r1  Qw = Wall heat transfer Tw = Wall temperature (K) R1= Inner radius of cylinder (m)



(13)



Tg  Tw (14) w  The total conductive resistanceQ(R) offered by the cylinder liner, piston rings, cylinder head, coating and piston R for the heat transfer from cylinder gases to coolant is given by the following equation        log e  r 2    log e r 3              1 1  r1    r2    R        h 2 r l  h 2 r l  k 2 l   k 2 l  1   3  c l l c c  g                3 log e  r 5    log  r 7         e   r4    r6     T p       2   k r 2 l r   k s 2 l s   2 r 7 k p         

(15)

l = Cylinder length (m), r1 = Inner radius of liner (m), r2 = Outer radius of liner (m), r3 = Outer radius of liner + Thickness of coating (m), r4 = Inner radius of piston ring (m), r5 = Outer radius of piston ring (m) r6 = Inner radius of piston skirt (m), r7 = Outer radius of piston skirt (m), kl = Thermal conductivity of liner (W/mK), kc = Thermal conductivity of coating (W/mK) kr = Thermal conductivity of piston ring (W/mK), ks = Thermal conductivity of piston skirt (W/mK) kP = Thermal conductivity of piston crown (W/mK), hg = Heat transfer coefficient of gas (W/m2K) hc = Heat transfer coefficient of coolant (W/m2K), TP = Thickness of piston crown (m) Mass of fuel injected Considering that nozzle open area is constant during the injection period, mass of the fuel injected for each crank angle is calculated using the following expression

   m f  C D An 2  f P    360 N 

(16)

An = Nozzle minimum area (m2), CD = Discharge coefficient, P = Density of fuel (kg/m3)  f = Pressure drop across the nozzle (N/m2),  = Nozzle open period in crank angle (degree) N = Engine speed (rpm) Nitric oxide formation Nitric oxide formation rate is given by 1 d NO  6 *1016   69090   exp O2 e 2 N 2 e dt T  T 

m  3.773 *  n   4  XN 2 P  TMP

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m  (  1) *  n   4  XO2 P  TMP

(19)

m  TMP  4.773 * n  1.443 * m  (  1) *  n   4 

(20)

4. Results and Discussion The performance and Emission characteristics of 60EPCY 20PI material coated combustion chamber diesel engine was investigated and compared with standard engine. 60EPCY 20PI material acts as a thermal barrier coating which can improve BSFC and increase thermal efficiency. UBHC and carbon monoxide emission are reduced compared to standard engine.The results obtained from the experiments conducted on the engine are presented in Figure3 to Figure 8. 600 Standard Engine 60EPCY 20PI Simulated Standard Engine Simulated 60EPCY 20PI

BSFC (g/kW-hr)

500 400 300 200 100 0

25

50

75

100

LOAD (%)

Fig. 3.Comparison of Brake Specific Fuel Consumption for different loads

Figure 3 shows the variations of brake specific fuel consumption of standard engine and compared with 60EPCY 20PI coated combustion chamber. The specific fuel consumption is reduced by 15.89% for resinPZT coated combustion chamber compare to standard engine. This may be due to increased temperature of the combustion chamber walls, which increases the temperature of the fuel issuing from the heated nozzle orifice resulting in the reduced fuel viscosity. 40 35

BTE (%)

30 25 20 Standard Engine 60EPCY 20PI Simulated Standard Engine Simulated 60EPCY 20PI

15 10 5 0 0

25

50 LOAD (%)

75

100

Fig. 4.Comparison of Brake Thermal Efficiency for different loads

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Vijaya Kumar K.R. et. al. / International Journal of Engineering Science and Technology Vol. 2(7), 2010, 2876-2885 The variation of brake thermal efficiency with load for engine operating on 60EPCY 20PI coated combustion chamber and standard engine are shown in figure 4. It is significant that modified combustion chamber has higher efficiency than that of base line. This may be due to thermal resistance on the walls which cannot allow the heat energy to the coolant. The maximum brake thermal efficiency obtained for engine operating on 60EPCY 20PI coated combustion chamber and standard engine are 33.05 % and 28.49 %.

80 70

Pressure (bar)

60 50 40 30 20 10 0 320

330

340

350

360

370

380

390

400

Crank Angle (degree) Standard Engine Simulated Standard Engine

60EPCY 20PI Simulated 60EPCY 20PI

Fig. 5. Pressure distribution in the engine cylinder at 1500 rpm for full load Pressure distribution in the engine cylinder at 1500 rpm for full load is shown in figure 5. The peak pressure of 60EPCY 20PI (79 bar @ 3640) is slightly advanced and attains the maximum peak pressure compared to the standard engine (70 bar @ 3700). This may be due to low thermal conductivity on the surface of the combustion chamber to the coolant.

Standard Engine 60EPCY 20PI Simulated Standard Engine Simulated 60EPCY 20PI

90 Heat Release Rate (J/deg CA)

80 70 60 50 40 30 20 10 0 -10330

340

350

360

370

380

390

400

410

Crank Angle (deg)

Fig. 6. Heat Release Rate in the engine cylinder at 1500 rpm for full load Figure 6 shows the heat release rate in the engine cylinder at 1500rpm for full load condition. Analysis of the data points revealed the ignition point was slightly advanced due to reduced ignition delay which causes more heat to be released before the top dead centre of the cylinder for 60EPCY 20PI compared to the standard engine. Figure 7 shows the comparison of hydrocarbon emission for different loads. Formation of sac volume is not possible because of high compression temperature at the end of compression stroke so the fuel droplets stored in the tip of the nozzle also enhance the combustion in the 60EPCY 20PI coated combustion chamber

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Vijaya Kumar K.R. et. al. / International Journal of Engineering Science and Technology Vol. 2(7), 2010, 2876-2885 which reduces hydrocarbon emission compared to standard engine. For modified combustion chamber and standard engine HC emissions are 0.23 g/kW-hr and 0.7 g/kW-hr at full load condition. 1.6

Standard Engine

1.4

60EPCY 20PI

UBHC (g/kW-hr).

1.2 1 0.8 0.6 0.4 0.2

Fig. 5.Comparison of Hydrocarbon emission for different loads

0

0

25

50

75

100

LOAD (%)

Fig. 7.Comparison of Hydrocarbon emission for different loads

Figure 8 indicated the variation of oxides of nitrogen with load for 60EPCY 20PI coated combustion chamber and standard engine. NOx is generated mostly from nitrogen present in air and also from fuel. The inherent availability of nitrogen and oxygen in the fuel accelerates the formation of NOx. While observing the trends of modified combustion chamber, it is noticed that higher the combustion and maximum temperature in the combustion chamber which in turn results in higher NOx. With 60EPCY 20PI coated combustion chamber, the NOx level varies from 6.57 g/kWh at no load and 3.72 g/kWh at full load condition. 7

Standard Engine

NOx (g/kW-hr)

6

60EPCY 20PI Simulated Standard Engine

5

Simulated 60EPCY 20PI

4

3

2 0

25

50

75

100

LOAD (%)

Fig. 8.Comparison of Oxides of Nitrogen emission for different loads

600

Standard Engine 60EPCY 20PI Simulated Standard Engine Simulated 60EPCY 20PI

500

0

EGT ( C)

400

300

200

100

0

0

25

50

75

100

LOAD (%)

Fig. 9.Comparison of Exhaust Gas Temperature for different loads

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Vijaya Kumar K.R. et. al. / International Journal of Engineering Science and Technology Vol. 2(7), 2010, 2876-2885 Figure 9 depicts the variation of exhaust gas temperature with load for 60EPCY 20PI coated combustion chamber and standard engine. It can be observed that when the combustion chamber is 60EPCY 20PI coated the combustion temperature is high which increases exhaust temperature. The increase in temperature is due to the better combustion of oxygenated fuels. The exhaust gas temperature for standard engine is 150oC at no load and 460oC at full load. With 60EPCY 20PI coated combustion chamber, the exhaust gas temperature increases to181oC to 590oC. 5

Standard Engine 4

CO (g/kW-hr)

60EPCY 20PI 3

2

1

0 0

25

50

75

100

LOAD (%)

Fig. 10.Comparison of carbon monoxide emission for different loads

The measured CO emissions for 60EPCY 20PI coated combustion chamber and standard engine are shown in Figure 10. The reduction in CO emission is due to complete combustion and on local rich region found in the 60EPCY 20PI coated combustion chamber. With 60EPCY 20PI coated combustion chamber, the CO level varies from 2.8 g/kWh at no load and 1.6 g/kWh at full load condition. 5. Conclusion A conventional contemporary diesel engine was converted to a 60EPCY 20PI coated combustion chamber diesel engine. The BSFC and emission were measured to determine the performance and emission characteristics of the engine. The following conclusions can be drawn from the experimental results. 60EPCY 20PI coated combustion chamber diesel engine shows better BSFC compared to conventional diesel engine. It is 15.89% reduced specific fuel consumption than the standard engine. NOx and Exhaust Gas Temperature are increased for 60EPCY 20PI coated combustion chamber diesel engine. Hydrocarbon emission was reduced by 52.1% in 60EPCY 20PI coated combustion chamber diesel engine. References [1] Cengiz Oner; Hanbey Hazar; Mustafa Nursoy. (2009): Surface Properties of CrN Coated Engine Cylinders. Material and Design, 30, pp. 914 -920. [2] Ganesan, N.; Ravikiran Kadoli. (2003): Buckling and Dynamic Analysis of Piezothermoelastic Composite Cylindrical Shell. Composite Structure, 59, pp.45-60. [3] Godfrey, D.J.; (1983): The Use of Ceramic for Engines. Material Design, 4, pp.759-765. [4] Hejwowski, T.; Weronski, A. (2002): The Effect of Thermal Barrier Coatings on Diesel Engine Performance. Vacuum, 65, pp.427-432. [5] Hwang, B.; Lee, S.; Ahn, J. (2002): Effect of oxides on wear resistance and surface roughness of ferrous coated layers fabricated by atmospheric plasma spraying, Material Science Engineering, 335, pp.268-280. [6] Krishnan, B. P.; Raman, N.; Narayanaswamy, K.; Rohatgi, K. P. (1980). Performance of an Al-Si-Graphite Particle Composite Piston in a Diesel Engine, Wear, 60, pp. 205-215. [7] Mallick, P.K. (1997). Composite Engineeringf Handbook, Marcel Dekker, Newyork. [8] Prasad, R.; Samria, N. (1990): Heat transfer and stress fields in the inlet and exhaust valves of a semi-adiabatic diesel engine, Comput Struct, 34, pp.765-777. [9] Tamilporai, P.; Jaichandar, S. (2004): The Status of Experimental Investigation on Low Heat Rejection Engines, SAE Paper No. 200401-1453. [10] Venkatesh, S. (1973): Surface treatment of Pistons and their effect on engine performance, Wear, 25, pp.65-71.

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