Engines with homogenous charge compression ignition (HCCI) are the low-temperature combustion models in which automatic oxidation reactions occur with the effect of in-cylinder pressure and heat at the end of preparation of homogenous air-fuel mixture and compression stroke within the cylinder by means of port injection or early direct injection. In-cylinder gas temperatures of such engines during the cycle are lower than conventional internal combustion engines. Therefore, they cause zero NOx and soot emissions. Moreover, the occurrence of combustion in very small crankshaft angles results in a decrease in heat losses observed in cylinder walls and an increase in thermal efficiency. Reducing mechanical friction is highly significant for increasing the effective productivity of HCCI engines. In internal combustion engines, 10% of total energy obtained from the fuel is spent on the heat emerging due to mechanical frictions. 20% of mechanical friction results from the friction occurring between piston ring and liners. In this article, frictional characteristics of compression ring (TOP) and piston skirt area have been examined for two different engine speeds and lubricants, by using technical properties of single-cylinder HCCI engine and in-cylinder pressure and temperature data obtained under full load by means of GT-SUITE software. As the increase in pressure, occurring inside the cylinder at the end of the exhaust stroke and at the beginning of intake stroke, increases ring pressure load in HCCI engines, higher level of piston ring frictions has been observed when compared to internal combustion engines with the same technical properties. Piston ring contact pressure force is a more effective parameter in terms of piston frictions, when compared to hydrodynamic pressure force. The use of lubricants with higher viscosity (SAE 10W-40) has enabled the piston to move more laterally. According to the analysis results, a maximum piston speed of 3.92 m/s for 800 rpm engine speed and 7.85 m/s for 1600 rpm engine speed has been obtained. Maximum friction power losses have been found as 63.84 W at 800 rpm engine speed and 85.91 W at 1600 rpm engine speed. Oil film thickness has obtained in the middle of the piston stroke in the intake, compression, power and exhaust strokes, respectively, 1.809, 1.674, 1.547 and 1.792 µm at 800 rpm engine speed and 1.101, 1.018, 0.932 and 1.119 µm at 1600 rpm engine speed.

In this study, a thermoelectric recovery system was designed to convert the exhaust waste heat of an internal combustion diesel engine directly to electric power and the performance was measured at different engine speeds in the unloaded state. The performances of two different thermoelectric generators were compared in a system designed using four modules. Maximum 0.92 W power was obtained for four modules at 3500 r/min, at an area of 0.0016 m2. Internal resistance of modules has increased according to the engine speed. The highest internal resistance obtained during the experiments is 11.69 Ω at engine speed of 3500 r/min. The characteristics of the overall thermoelectric generator performance is coherent with the analysis model. In the current graph according to engine speed, the maximum absolute error is calculated for modules TEG 12-8 and TEG1-199 as 0.010 and 0.044, respectively (at experimented 3500 r/min). To charge the battery under maximum power point conditions, 133 thermoelectric modules were required (TEG1-199). Maximum power transfer is obtained when the load resistor is connected in parallel at 10 Ω. It is seen that modular structure thermoelectric generators are more important alternative than Rankine cycle system in terms of waste heat recovery, despite thermoelectric system has low efficiency.

In this study, design of tube type linear generator, which can generate electricity from suspension systems of electrical vehicles, has been realised. Information about widely-used suspension systems has been given and advantages and disadvantages of linear type electro-magnetic dumpers have been mentioned. Analytic design of tube type linear generator has been made for passive suspension system. In line with obtained sizing parameters, numerical analyses have been made in Ansys-Maxwell programme and results of such analyses have been examined. Prototype of analyzed tube type linear generator has been made. Measurements of magnetic flux density and simulation results in air gap have been compared. The linear generator designed has been applied for passive suspension. The experiments of the linear generator with 20, 40, 60, 80, 100, 120 and 130 mm stroke length were performed, respectively. During the experiments, a frequency range of 1 Hz to 5 Hz was chosen. The highest speed was 1,3 m/s and the generated pk-pk voltage value was 37.7 volts. The speed value of the generator changes according to the road condition. Therefore, a converter is needed for battery charging after the generator output voltage is rectified.

In this study, examination of the temperature distribution for three different heat exchanger models for exhaust gas waste heat recovery systems to be used in internal combustion motorcycle engines has been made. Simulations of the models have been made by means of ANSYS Workbench Fluent software and comparative results have been put forward. It has been taken into consideration that the selected heat exchanger models have generable geometries. Model no. 1 is inclined to the outlet from the inlet by 5o, model no. 2 has three steps each of which has a gradient of 20o, and model no. 3 has a fixed section width which is parallel to exhaust gas transfer. Moreover, in model no. 3, a heat sink has been placed into the exhaust gas. On cold surfaces, the highest and the lowest temperatures have been measured respectively as 337.937K and 329.465K in model no. 1, as 342.875K and 329.639K in model no. 2, and as 363.897K and 354.995K in model no. 3. The difference between the lowest and the highest temperatures is observed as in models no. 2 and 3. With relation to the temperature distributions on hot surfaces of TEGs, the lowest and the highest temperatures are respectively as 508.631 K and 402.742 K in model no. 1, as 510.092 K and 409.632 K in model no. 2, and as 536.595 K and 510.633 K in model no. 3 It has been observed that the lowest difference of temperature occurred in model no. 3. When the results are examined, it is seen that the best temperature difference and the highest temperature value have been achieved in model no. 3.

Bu çalışmada, 2 zamanlı içten yanmalı 49 cc'lik bir benzinli motor basınçlı hava ile çalışır hale getirilmiştir. Havanın silindir içerisine gönderilmesinde, bir elektromanyetik supaptan faydalanılmıştır. Elektromanyetik supabın kontrolü için Atmega8 mikrodenetleyicisinin kullanıldığı bir elektronik kontrol devresi tasarlanmış ve imal edilmiştir. Basınçlı hava, silindir içerisine farklı emme supap zamanlamalarında gönderilmiş ve motor performans değerleri karşılaştırılmıştır. Sonuçta elektronik kontrol devresi elektromanyetik supabı yaklaşık olarak 1600 1/min motor hızı için başarılı bir şekilde kumanda ettiği görülmüştür.