**4.1 Experimental setup**

206 Ceramic Coatings – Applications in Engineering

those studies. Uzun et. al. (1999), Beg et. al. (1997), Taymaz et. al. (2003), Marks and Boehman (1997), Schwarz et. al. (1993) and Hejwowski (2002) can be referred for these studies. Alternatively, Sun et. al. (1994), proposed silicon nitride (HPSN) piston materials and thick coating layers of plasma sprayed zirconia between 2-7 mm for cylinders.

Specific literature survey was resulted that specific fuel consumption, heat rejection from cylinders and NOx emissions are the most reported results of experimental and numerical studies for ceramic coated engines. Depending on rising in cylinder temperatures, almost all studies expressed an increase in NOx emissions. This event can be named as the main side effect of ceramic coating or thermal barrier coating of internal combustion engines. The increase in NOx emissions is observed between 10-40% from the literature. Gataowski (1990), Osawa et. al. (1991) and Kamo et. al. (1999) some of the papers in which these aforementioned results can be found. However there are some suggestions for reducing this increase by changing injection timing or decreasing advance angle. Winkler and Parker (1993) reported 26% decrease in NOx emissions of thermal barrier coated engine by changing injection timing. Similarly Afify and Klett (1996), stated that 30% decrease in NOx emissions was achieved by advance adjustment. When specific fuel consumption is considered, results are varying both negatively and positively. This is particularly the result of volumetric and combustion efficiency. Specific fuel consumption decrease can be observed from the literature between 1- 30%. Ramaswamy et. al. (2000), reported 1-2% specific fuel consumption decrease while Bruns et. al. (1989), stated specific fuel consumption decrease between 16-37% by means of ceramic thermal barrier coating. On the contrary, Sun et. al. (1993) and Beg et. al. (1997) expressed 8% increase in specific fuel consumption by the utilization of ceramic thermal barrier coating. Similarly Kimura et. al. (1992), specified that thermal barrier coating resulted 10% increase in specific fuel consumption. As desired, ceramic thermal barrier coatings were resulted as a decrease between 5-70% in heat rejection from cylinders to engine block and cooling system. Vittal et. al. (1997) reported 12% decrease in transferred heat from cylinders and Rasihhan and Wallace (1991) informed that heat rejection rate was decreased between 49,2-66,5% after

There are several more indicators that show effectiveness of ceramic thermal barrier

In this study, the effects of ceramic coating of combustion chamber of a turbocharged diesel engine to engine performance and exhaust emissions were investigated. Increasing mechanical energy by preventing heat losses to coolant and reducing cooling load, improving combustion by increasing wall temperatures and decreasing ignition delay, more power attaining in turbocharged engines by increasing exhaust gas temperatures and decreasing carbon monoxide and soot are aimed. For this aim, cylinder head, inlet and exhaust valves and pistons of the engine were coated with 0.5 mm zirconia by plasma spray coating. Then, the engine was tested for different brake loads and speeds at standard, ceramic coated engine one and ceramic coated engine 2 conditions. The results gained from the experimental setup were analyzed with a computer software and presented with comparatively graphics. Briefly,

**4. A case study: The effects of Y2O3 with coatings of combustion chamber surface on performance and emissions in a turbocharged diesel engine** 

coatings. Further search can be conducted for specific parameters.

Matsuoka and Kawamura (1993) used Si3N4 instead of zirconia.

ceramic coating.

Appropriate measurement equipment, their calibration and operational conditions have an important effect on experimental results. Engine specifications are given in Table 4. Experiments were conducted in internal combustion engines workshop in Gazi University Technical Education Faculty Mechanical Education Department Turkey. Cross section view of the engine is shown in Fig. 6 and solid model view of experimental setup is illustrated in Fig. 7.


Table 4. Specifications of engine used in experiments

Fig. 6. Cross sectional view of test engine

Ceramic Coating Applications and Research Fields for Internal Combustion Engines 209

b) Charge air flow measurement unit and damper

measurement device

Air flow measurement device used in the experiments is GO-Power M5000 type. A manometer was placed onto the device and it has a gauge glass of 0-75 mm long. For the conducted experiments, a 2.75 inch nozzle was attached to entrance of damper. Ohaus brand digital mass scale with 0.1 gram sensibility and 8 kg capacity was preferred for determining fuel amount. For exhaust emission, two different exhaust emission measurement devices were used during experiments as it can be seen from Fig. 7 and Fig. 8. For measuring carbon monoxide, carbon dioxide, nitrogen oxides, oxygen and sulphur oxides as ppm (particle per million) and mg/m3, Gaco-SN branded exhaust gas analyser device was used. It can also calculate combustion efficiency and excess air coefficient. For determining smoke intensity, OVLT-2600 type diesel emission measurement device was used. This device can measure smoke amount as *k* factor

and percentage. Measurement range and accuracy of OVLT-2600 are given in Table 5.

Fig. 8. Measurement devices in experimental setup for determining exhaust emissions and

c) Orifice plate for measuring coolant flow rate

> f) Temperature measurement screen

a) Control panel

performance characteristics

d) Exhaust gas analyser e) Smoke intensity

Fig. 9. Three different views of the test engine

Fig. 7. Solid model view of experimental setup

Measurement devices were used for determining both exhaust emission values and performance characteristics. Photographs of these devices are given in Fig. 8. Experimental setup consist of basic units such as hydraulic brake dynamometer, cooling tower for cooling engine coolant, fuel consumption measurement device, temperature and pressure probes and control panel.

Engine was loaded by hydraulic dynamometer which is connected to engine with a shaft during experiments. Fig. 9 shows test engine in experimental setup. Additionally, flow rate measurement setups were utilized in the system for charge air and coolant.

a) Control panel

208 Ceramic Coatings – Applications in Engineering

Measurement devices were used for determining both exhaust emission values and performance characteristics. Photographs of these devices are given in Fig. 8. Experimental setup consist of basic units such as hydraulic brake dynamometer, cooling tower for cooling engine coolant, fuel consumption measurement device, temperature and pressure probes

Engine was loaded by hydraulic dynamometer which is connected to engine with a shaft during experiments. Fig. 9 shows test engine in experimental setup. Additionally, flow rate

measurement setups were utilized in the system for charge air and coolant.

Fig. 7. Solid model view of experimental setup

and control panel.

b) Charge air flow measurement unit and damper

c) Orifice plate for measuring coolant flow rate

d) Exhaust gas analyser e) Smoke intensity measurement device

f) Temperature measurement screen

Fig. 8. Measurement devices in experimental setup for determining exhaust emissions and performance characteristics

Air flow measurement device used in the experiments is GO-Power M5000 type. A manometer was placed onto the device and it has a gauge glass of 0-75 mm long. For the conducted experiments, a 2.75 inch nozzle was attached to entrance of damper. Ohaus brand digital mass scale with 0.1 gram sensibility and 8 kg capacity was preferred for determining fuel amount. For exhaust emission, two different exhaust emission measurement devices were used during experiments as it can be seen from Fig. 7 and Fig. 8. For measuring carbon monoxide, carbon dioxide, nitrogen oxides, oxygen and sulphur oxides as ppm (particle per million) and mg/m3, Gaco-SN branded exhaust gas analyser device was used. It can also calculate combustion efficiency and excess air coefficient. For determining smoke intensity, OVLT-2600 type diesel emission measurement device was used. This device can measure smoke amount as *k* factor and percentage. Measurement range and accuracy of OVLT-2600 are given in Table 5.

Fig. 9. Three different views of the test engine

Ceramic Coating Applications and Research Fields for Internal Combustion Engines 211

In diesel engines, power output, torque and fuel consumption values according to engine speeds are named as engine characteristics. Differences in these characteristics at different load and engine speeds are illustrated with graphical curves. These curves are called as characteristic curves. Engine characteristic curves provide important information about engine performance at real time operational circumstances. Experimental measurements not always give directly the desired data. These data should be calculated using experimental measurements. Experimental measurements generally consist of torque, engine revolution rate, fuel consumption, charge air flow rate, coolant flow rate, ambient temperature, pressure and humidity, exhaust gases temperatures, coolant entrance and exit temperatures. The most important performance characteristics calculated from these measurements are effective power, torque, mean effective pressure and specific fuel consumption (Ciniviz,

a) Cylinder heads and valves without coating b) Ceramic coated cylinder heads and valves

During experiments, intake and exhaust valve adjustments were made according to engine catalogue values and injectors were tested at 200 bar injection pressure. Piston rings were renewed. To measure exhaust gas composition, exhaust pipe was drilled after one meter distance from exhaust pipe entrance and measurement probe was fitted to the hole. Experiments were conducted at ten different engine speeds changing between 1100 rev/min and 2800 rev/min and seven different brake loads changing between 40 Nm and full load.

Fig. 11. Cylinder head and valves before coating and after coating

2005).

Fig. 10. Ceramic coated piston tops


Table 5. OVLT-2600 measurement ranges and accuracies

1 0C accuracy thermometer which have 130 0C gauge and Precision branded barometer which has measurement range of 710-800 mmHg were used during experiments. A chronometer with 0.01 second resolution was employed while fuel consumption rate was measuring.
