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Doğalgaz yakıtlı HCCI bir motorda hidrojen ilavesinin yanma karakteristikleri üzerindeki etkilerinin nümerik olarak incelenmesi
(BİLEŞİM Yayıncılık, 2015) Polat, Seyfi; Uyumaz, Ahmet; İpci, Duygu; Yücesu, Hüseyin Serdar; Solmaz, Hamit; Yılmaz, Emre
Homojen dolgulu sıkıştırma ile ateşlemeli motorlar konvansiyonel içten yanmalı motorlarla karşılaştırıldığında yüksek termik verim, NOx ve is emisyonlarındaki eş zamanlı azalma avantajlarından dolayı yeni bir araştırma alanı olmuştur. HCCI motorlarda kendi kendine tutuşma zamanlaması üzerinde direkt kontrol olmadığından çalışma ve yük aralığı sınırlı kalmaktadır. Yanma işlemini etkileyen en önemli parametrelerden bazıları karışımın kompozisyonu ve yakıtın kimyasal özellikleridir. Bu çalışmada sıkıştırma oranı 10:1 olan doğal emişli, tek silindirli, dört zamanlı, dört supaplı, doğal gaz ile çalışan bir HCCI motorunda hidrojen ilavesinin yanma işlemi üzerindeki etkileri açık kaynak kodlu KIVA-4 yazılımı ile nümerik olarak incelenmiştir. Bu amaçla doğalgaz yakıtının içerisine %0, %10, %20, %30,%40, oranlarında hidrojen ilave edilerek beş farklı yakıt karışımı hazırlanmıştır. Bununla birlikte yanma analizi üç farklı hava fazlalık katsayısı değerinde (?=1.5, ?=2, ?=2.5) gerçekleştirilmiştir. Sonuçta, hidrojen ilavesinin kendi kendine tutuşma zamanlaması, toplam yanma süresi, ısı dağılımı, silindir içi basınç ve silindir içi sıcaklık üzerindeki etkileri araştırılmıştır.
The Effects of iso-propanol and n-heptane Fuel Blends on HCCI combustion characteristics and engine performance
(2015) İpci, Duygu; Yılmaz, Emre; Aksoy, Fatih; Uyumaz, Ahmet; Polat, Seyfi; Solmaz, Hamit
In this study, the effects of iso-propanol fuel blends were investigated on HCCI combustion and engine performance. The variations of cylinder pressure, heat release rate, start of combustion and engine performance were studied in a single cylinder, four stroke, gasoline HCCI engine. The experiments were conducted at different inlet air temperatures at constant air excessive coefficient (λ=2) and engine speed (1500 rpm). The test results showed that cylinder pressure and heat release rate delayed with the addition of iso-propanol in the test fuels. It was also found that the increase of inlet air temperature causes to advance the combustion. Iso-propanol has higher octane number compared to conventional fuels. However, calorific value of iso-propanol is lower than conventional fuels. The aim of this study is to research the usage of iso-propanol in HCCI engines. The experimental findings showed that the tendency of knocking combustion decreased with the increase of the amount of iso-propanol. The start of combustion was delayed with the increase of the amount of iso-propanol. In addition, combustion duration decreased with the addition of iso-propanol in HCCI combustion. As a result, knocking can be prevented using iso-propanol in HCCI engines. This effect also led to extend the HCCI operating range
Reaktif kontrollü sıkıştırma ile ateşlemeli (RCCI) bir motorda lamdanın yanma karakteristiklerine etkileri
(Afyon Kocatepe Üniversitesi, 2017) Uyumaz, Ahmet; Solmaz, Hamit; Boz, Fahrettin; Yılmaz, Emre; Polat, Seyfi
Bu çalışmada reaktif kontrollü sıkıştırma ile ateşlemeli (RCCI) bir motorda lamdanın (?) yanma karakteristikleri üzerindeki etkileri deneysel olarak incelenmiştir. Dört zamanlı, dört silindirli benzinli bir motor tam yük şartlarında referans yakıt PRF40 (Primary reference fuel, %40 porttan izooktan, %60 direkt n-heptan) kullanılarak ?=0.83, ?=0.88, ?=1, ?=1.24, ?=1.61 ve ?=2.65 lamda değerlerinde sabit 40°C emme giriş sıcaklığı ve 1000 d/d motor devrinde çalıştırılmıştır. RCCI yanma modunda yanma karakteristikleri, indike termik verim, net iş, kümülatif ısı yayılımı ve özgül yakıt tüketiminin değişimleri incelenmiştir. Deneysel çalışmalar sonucunda karışımın zenginleşmesi ile yanmanın rötara alındığı görülmüştür. Maksimum silindir içi basınç ?=0.83 ile elde edilmiştir. Lamda arttıkça indike termik verimin arttığı, özgül yakıt tüketiminin azaldığı görülmüştür. Maksimum indike termik verim ?=1.61'da %38.36 olarak belirlenmiştir. Karışımın daha da fakirleştirilmesi (?=2.65) termik verimin azalmasına neden olmuştur. Test sonuçları aynı zamanda karışım fakirleştikçe çevrimsel farklılıkların arttığını, maksimum çevrimsel farklılığın ?=2.65 değerinde %5.91 olduğunu göstermiştir. RCCI motorda lamdanın yanma karakteristikleri ve yanma süresi üzerinde kayda değer etkilerinin olduğu görülmüştür
Bir dizel motorunun bilgisayar yardımı ile termodinamik ve performans analizi
(Gazi Üniversitesi, 2013) Polat, Seyfi; Solmaz, Hamit; Yücesu, Hüseyin Serdar; Uyumaz, Ahmet
Bu çalışmada, dört zamanlı, tek silindirli, normal emişli, direkt püskürtmeli bir dizel motorunun çevrim analizi için MATLAB programında bir simülasyon geliştirilmiştir. Simülasyon sonucunda; tam yükte krank mili açısına bağlı olarak farklı motor hızlarında (1000–4000 d/d), farklı sıkıştırma oranlarında (16,20,24) ve farklı hava fazlalık katsayılarında (1.3,1.5,1.7) silindir basıncı, sıcaklık ve motor performans eğrileri elde edilmiştir. 1.5 hava fazlalık katsayısı değerinde sıkıştırma oranı arttıkça silindir içi basıncın arttığı, ısı dağılımının azaldığı görülmüştür. Sıkıştırma oranı 20 değerinde hava fazlalık katsayısı arttıkça silindir içi basınç ve ısı dağılımının azaldığı görülmüştür. Sıkıştırma oranı ve hava fazlalık katsayısının silindir içi yanma işlemini ve motor performansını etkilediği görülmüştür. Sonuçta, sıkıştırma oranı arttıkçamotor performansının artmış, hava fazlalık katsayısı arttıkça azalmıştır.
Üç-fazlı dizel emülsiyon yakıtlarının motor performansı ve egzoz emisyonlarına etkisi
(Gazi Üniversitesi, 2013) Yılmaz, Emre; Solmaz, Hamit; Polat, Seyfi; Altın, Murat
Dizel motorları düşük yakıt tüketimlerinden dolayı hem kara hem de deniz taşımacılığında yaygın şekilde kullanılmaktadırlar. Ancak dizel motorlarından kaynaklanan zararlı azot oksit (NOx) ve is emisyonları insan sağlığını tehdit etmektedir. Dizel emisyonlarının azaltılabilmesi için pek çok araştırma yapılmıştır. Belirli oranlarda su içeren dizel emülsiyon yakıtları zararlı egzoz emisyonlarını önemli ölçüde azaltabilmektedirler. Bu nedenle emülsiyon yakıtlar son yıllardaki önemli araştırma alanlarından birisi olmuştur. Bu çalışmada % 10 (E1) ve % 15 (E2) su ihtiva eden dizel emülsiyon yakıtlarının motor performansı ve egzoz emisyonları üzerine etkileri incelenmiştir. Diğer çalışmalardan farklı olarak yakıtların elde edilmesinde su çözücü olarak % 1 oranında yardımcı emilgatör mono etilen glikol kullanılmıştır. E1 emülsiyonunun egzoz emisyonlarını kısmen azaltırken motor performansını da önemli ölçüde azalttığı belirlenmiştir. E2 emülsiyonunun kullanılmasıyla karbon monoksit (CO), NOx ve is emisyonlarında sırasıyla % 45,9, % 26,9 ve % 18,8 azalmıştır. Buna karşılık motor momenti % 15,72 azalmıştır.
Investigation of usability of the fusel oil in a single cylinder spark ignition engine
(Elsevier B.V., 2015) Calam, Alper; Solmaz, Hamit; Uyumaz, Ahmet; Polat, Seyfi; Yılmaz, Emre; Içingür, Yakup
In order to decrease the dependency on petrol-originated energy resources, the utilization of different energy resources in internal combustion engines has been the center of interest of researchers. The main renewable alternative combustible species are ethanol, methanol, hydrogen, biodiesel, and biogas. On the other hand, appearing as a by-product during alcohol production via fermentation, the fusel oil is another alternative energy resource which can be used in internal combustion engines. Containing high alcohols, fusel oil is dark brown colored alcohol mixture, and has a strong odor. The calorific value of fusel oil close to other alternative combustible types ones and the limited number of researches on utilization of fusel oil, an alcohol derivative, in internal combustion engines constitute the base of this research. In this study, the effects of the mixture of unleaded gasoline and fusel oil on engine torque, brake specific fuel consumption and exhaust emissions in a single cylinder, spark ignition engine having port-type fuel infection system at various engine speeds and loads have been investigated. As a result of research carried out, as the amount of fusel oil in mixture increased, the improvements have been observed in engine torque at all of engine speeds and loads compared to pure unleaded gasoline. It has been determined that the brake specific fuel consumption and carbon monoxide (CO) and hydro-carbon (HC) emissions have increased while nitrogen-oxide (NOx) emissions have decreased. © 2014 Energy Institute. Published by Elsevier Ltd. All rights reserved.
Mapping of an HCCI engine using negative valve overlap strategy
(Taylor and Francis Inc., 2020) Polat, Seyfi; Solmaz, Hamit; Yılmaz, Emre; Calam, Alper; Uyumaz, Ahmet; Yücesu, Hüseyin Serdar
In order to control combustion phasing and extend operation range of homogeneous charged compression ignition (HCCI) engines, several techniques such as controlling inlet air temperature and pressure, using alternative fuels, variable compression ratio, supercharging, etc. have been applied. Among them, variable valve mechanism received much attention to extend HCCI operating range and control autoignition. Mode switching between spark plug ignition (SI) to HCCI has been started to use widely because of limited operation range of the HCCI mode. To control of an engine switching combustion modes between SI and HCCI, embedded system needs parametrical control maps of the engine. In this study, operation range, air excess ratio, torque and thermal efficiency maps of an HCCI engine using negative valve overlap (NVO) strategy were obtained and additionally the effects of NVO on HCCI combustion in view of in-cylinder temperature, heat release rate, effective thermal efficiency, combustion phasing, and exhaust emissions were investigated. Also, variation of CO, HC, and NOx emissions were evaluated at different valve overlaps. Three different valve overlap including +8, ?8, and ?16 CA were used in the experiments. Test results showed that in-cylinder pressure and heat release decreased with NVO. The test engine could run without knocking by application of NVO. It was seen that operating range of HCCI extended with NVO. It was also found that effective thermal efficiency increased with ?16ºCA valve overlap compared to other valve timings.
A numerical study on the effects of EGR and spark timing to combustion characteristics and NOx emission of a GDI engine
(Taylor and Francis Inc., 2016) Polat, Seyfi; Uyumaz, Ahmet; Solmaz, Hamit; Yılmaz, Emre; Topgül, Tolga; Yücesu, Hüseyin Serdar
EGR is one of the most significant strategies for reducing especially nitrogen oxides (NOx) emissions from internal combustion engines. The thermal efficiency of spark ignition engines is lower than compression ignition engines because of its lower compression ratio. If the compression ratio is increased to obtain higher thermal efficiency, there may be a knocking tendency in spark ignition engines. EGR can be used in order to reduce NOx emissions and avoid knocking phenomena at higher compression ratios. In-cylinder temperature at the end of combustion is decreased and heat capacity of fresh charge is increased when EGR applied. Besides EGR, spark timing is another significant parameter for reducing exhaust emissions such as nitrogen oxides, and unburned hydrocarbon (UHC). In this study the effects of EGR and spark timing on spark ignition engine were investigated numerically. KIVA codes were used in order to model combustion process. The combustion process has been modeled for a single cylinder, four stroke and gasoline direct injection (GDI) spark ignition engine. The results showed that in-cylinder pressure and heat release rate decrease as EGR ratio increase. In-cylinder pressure increases with the advancing of spark timing. Advancing spark timing increases the heat release rate and in-cylinder temperature. The simulation results also showed that EGR reduced exhaust gas temperature and NOx emissions. © 2015 © 2015 Taylor & Francis.
A thermodynamic approach to compare the performance of rhombic-drive and crank-drive mechanisms for a beta-type Stirling engine
(Elsevier Ltd, 2016) Aksoy, Fatih; Solmaz, Hamit; Karabulut, Halit; Çınar, Can; Özgören, Yaşar Önder; Polat, Seyfi
In this study, the effect of rhombic drive and crank drive mechanisms on the performance of a beta-type Stirling engine was investigated by nodal analysis. Kinematic and thermodynamic relations for both drive mechanisms were introduced and a Fortran code was written for the solution. Piston strokes, cylinder and displacer diameters, hot and cold end temperatures, regenerator volumes and heat transfer surface areas were taken equal for both engines with two different drive mechanisms. In the analysis, air was used as the working gas. Engine power and efficiency were compared for different charge pressure values, working gas mass values, heat transfer coefficients and hot end temperatures. Maximum specific engine power was 1410 W/L for the engine with rhombic drive mechanism and 1200 W/L for the engine with crank drive mechanism at 4 bars of charge pressure and 500 W/m2K heat transfer coefficient. Rhombic drive mechanism was relatively advantageous at low working gas mass values and high hot end temperatures. In comparison with the engine having rhombic drive mechanism, the relatively poor kinematic behaviour of the engine having crank drive mechanism caused lower engine efficiency and performance. Heat transfer coefficient was also predicted by using an experimental pressure trace. © 2015 Elsevier Ltd.
Combustion and performance characteristics of an HCCI engine utilizing trapped residual gas via reduced valve lift
(Elsevier Ltd, 2016) Çınar, Can; Uyumaz, Ahmet; Polat, Seyfi; Yılmaz, Emre; Can, Özer; Solmaz, Hamit
In this study, the effects of residual gas fraction (RGF) on homogeneous charged compression ignition (HCCI) combustion were investigated experimentally. Experiments were performed at different lambda values and constant intake air temperature of 80 °C with the blend of 20% n-heptane and 80% isooctane (PRF80) test fuel. In order to obtain exhaust gas trapping and HCCI operation, two different cam mechanisms, having reduced valve lift, were used. Valve lift values of 5.5 mm (In5.5) and 3.5 mm (In3.5) were used in cam mechanisms. Exhaust valve lift values were 3.5 mm (Ex3.5) for both cam mechanisms. The experimental findings showed that in-cylinder pressure and heat release rate decreased using In5.5-Ex3.5 cam mechanism compared to In3.5-Ex3.5. More residual gases were trapped using In3.5-Ex3.5 cam mechanism. Combustion was also retarded with low lift cams due to more trapped residual gases. Indicated thermal efficiency was found 28.4% with In 3.5-Ex 3.5 whereas obtained 33.57% with In 5.5-Ex 3.5 cam mechanism at 1000 rpm. RGF was computed as 20.12% and 21.12% with In 5.5-Ex 3.5 and In 3.5-Ex 3.5 cam mechanisms, respectively, at 1000 rpm engine speed and stoichiometric air/fuel ratio. Moreover, indicated thermal efficiency was found to be higher about 17.91% with In 5.5-Ex 3.5 according to In 3.5-Ex 3.5 at 1200 rpm. Consequently, it was observed that HCCI combustion phasing can be controlled using low lift cams. It was seen that trapping exhaust gases in the cylinder is a feasible and practical method to control combustion phasing and spread out the HCCI operating range. In addition, stable HCCI combustion can be achieved trapping exhaust gases resulting in avoiding knocking especially at high engine loads. © 2016 Elsevier Ltd. All rights reserved.
An experimental study on the effects of diesel and jet-A1 fuel blends on combustion, engine performance and exhaust emissions in a direct injection diesel engine
(Turkish Society for Thermal Science and Technology, 2016) Solmaz, Hamit; Yamık, Hasan; Uyumaz, Ahmet; Polat, Seyfi; Yılmaz, Emre
In this study, an experimental investigation was performed in order to determine the effects of Jet-A1(A100), diesel fuel and Jet-A1/diesel fuel blends (A25, A50, A75) including 25% Jet-A1/75% diesel, 50% Jet-A1/50% diesel and 75% Jet- A1/25% diesel by volume respectively on combustion and engine performance in a single cylinder, direct injection diesel engine. For this purpose, the test engine was run at four different brake torques (7.5, 11.25, 15 and 18.75 Nm) at maximum brake torque engine speed (2200 rpm). The variation of cylinder pressure, heat release rate, ignition delay, combustion duration and exhaust emission were investigated in a naturally aspirated direct injection diesel engine fueled with diesel-Jet-A1 fuel blends. The test results showed that ignition delay time decreased with the increase of brake torque. Maximum in-cylinder pressure was retarded versus crank angle with the increase of brake torque. NO x emissions decreased with the increase of amount of Jet-A1 in the test fuels, but CO and soot emissions increased. It was also found that combustion duration increased when Jet-A1 (A100) fuel was used compared to A25, A50, A75 test fuels. In conclusion, Jet-A1 aviation fuel can be utilized via mixing with diesel fuel in diesel engines.
An experimental study on combustion, engine performance and exhaust emissions in a HCCI engine fuelled with diethyl ether-ethanol fuel blends
(Elsevier, 2016) Polat, Seyfi
In this study, the effects of diethyl ether–ethanol fuel blends on HCCI combustion, engine performance and exhaust emissions were investigated experimentally in a single cylinder, port injection HCCI engine. In the experiments, ethanol and diethyl ether mixtures in different ratios by volume such as 30% ethanol–70% diethyl ether (E30/D70), 40% ethanol–60% diethyl ether (E40/D60), 50% ethanol–50% diethyl ether (E50/D50) and 100% diethyl ether (DEE) were used as test fuels. A single cylinder Ricardo Hydra test engine was converted to a HCCI engine, increasing the compression ratio and the warming inlet air temperature. The experiments were conducted at the engine speed of 1200 rpm and at different lambda values. The inlet air temperatures were selected as 333, 353, 373 and 393 K. The variation of cylinder pressure, heat release rate, duration of combustion, starting of combustion, indicated mean effective pressure, thermal efficiency and the emissions of carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxides (NOx) were investigated in this study. The results showed that the test engine could not be operated at leaner mixtures with the increase of the amount of ethanol in the test fuels because of the higher octane number and higher auto-ignition temperature of ethanol. Besides the lower in-cylinder pressure and the heat release rate were obtained with the increase of lambda for all test fuels. It was observed that the duration of combustion increased with the increase of the inlet air temperature. Test results also showed that the combustion of HCCI was advanced with the increase of the inlet air temperature. The starting of combustion was delayed with the increase of the amount of ethanol in the test fuel. Indicated mean effective pressure increased by about 23% and was obtained as 2.98 bar for E40/D60 as compared to E30/D70 at ? = 2 and at 353 K inlet air temperature with the addition of ethanol. Indicated thermal efficiency increased by about 23.1% and was obtained as 33.1% at ? = 2 with DEE as compared to E30/D70 at that lambda. Almost zero NOx emissions were obtained for E30/D70 and E40/D60 test fuels. Consequently, it was seen that diethyl ether and ethanol fuel blends had a remarkable effect on HCCI combustion, engine performance and exhaust emissions.

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