Disel motorların değişken yük koşullarında bilgisayar yardımı ile incelenmesi
Computer aided simulation of diesel engines linder variable load conditions
- Tez No: 46348
- Danışmanlar: PROF.DR. OSMAN KAMİL SAĞ
- Tez Türü: Yüksek Lisans
- Konular: Gemi Mühendisliği, Marine Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1995
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 54
Özet
ÖZET Sunulan çalışmanın amacı dizayn edilmiş bir diesel motorun değişken yük koşullarında bilgisayar yardımı ile simülasyonunu sağlamak ve değişken valf zamanlamalarının motor performansına etkilerini belirlemektir. Çalışmada SAG[1] tarafından geliştirilen ve diesel motorların emme ve egzost peryodlannda türboşarjerlerde, emme ve egzost manifoldlannda ve silindirlerde oluşan zamana bağlı gaz akımını“homentropik olmayan akım modeli”ile simüle eden bir bilgisayar programı kullanılmıştır. Programın gelişimindeki aşamalar ve literatürde bugüne kadar yapılan çalışmalar Bölüm 2 'de ele alınmıştır. Bölüm 3'te ise modelleme teorisi açıklanmıştır. Modelleme teorisi, diesel motorların emme ve egzost manifoldlannda meydana gelen gaz akımının zamana bağlı tek boyutlu ve gaz zerrecikleri arasında değişken entropiye sahip olarak dalgalar halinde ilerlediği düşüncesine dayanmaktadır. Süreklilik denklemi, momentum denklemi ve genel enerji denkleminden hareket ederek elde edilen lineer olmayan, hiperbolik kısmi diferansiyel denklemler, sınır koşulları teorilerinden de yararlanarak karakteristik yöntemi ile çözülmektedir. Bölüm 4' de açıklanan bilgisayar programı, Bölüm 5 'de belirtildiği şekilde, 1500 rpm'de 1880 kW güç üretebilen bir istasyoner motor jeneratör grubuna (MTU 396 TB34D) uygulanmış ve bugüne kadar yapılan çalışmalardan farklı olarak bir diesel motorun değişken yük koşullarında simülasyonu basan ile gerçekleştirilmiştir. Bölüm 6'da ise değişken yük koşullarında farklı valf zamanlamalarının motor performansına etkileri araştırılmış ve elde edilen sonuçlar Bölüm 7' de sunulmuştur. Çalışmayı bir araya toplayabilmek için bilgisayar programlan, giriş dosyaları, simülasyon sonucu, çizdirilen grafikler ve elde edilen sonuç dosyalan Ek'lerde verilmiştir. XVI
Özet (Çeviri)
COMPUTER AIDED SIMULATION OF DD2SEL ENGINES UNDER VARIABLE LOAD CONDITIONS SUMMARY Diesel engines have become the most widely preferred power sources of the industry and marine applications, both as the prime mover and electrical generator driver. The search for competitiveness with alternate power sources have led diesel engine manufacturers to produce more power from smaller sized engines. The main targets have been identified as reducing the initial cost, reducing the maintenance and operation costs and producing high performance engines with lower specific power consumption. Extensive research and development work on high speed, supercharged and modular diesel engines is still under progress. The main topics where this research and development work is concentrated on the combustion chamber geometry in order to burn the fuel in the most effective manner, models of combustion, reduction of NOx emissions, the structure of inlet and exhaust systems and for increasing the air charge. When experimental methods for the design of diesel engines are used, both the laboratory work and the design of the prototype become more time consuming and demand for a longer time. Present day design work more relies on computer simulation suites which model the diesel engine in a realistic way. Those numerical methods, which include CAD/CAM and CAE enable the designer to investigate the subsystems of the diesel engine separately and the effects of the most minute changes in the design parameters on the engine performance are predicted realistically. This research employs the computer aided simulation of a pre-designed diesel engine with variable load conditions and the effects of variable valve timing on the engine performance. This computer software used is the program developed by SAG[1] which simulates the time-dependent flow during the intake and exhaust phases at the turbocharger, intake and exhaust manifolds and the cylinders based on a“non- homentropic flow model”. Present day knowledge on the modeling of diesel engines together with their intake and exhaust manifolds, combustion chamber and turbochargers from the point of view of gas dynamics is based on the research work performed by numerous researchers using different methods of approach. The stages on the development of program and research work done so far in this field as appears in free literature are summarized in Chapter 2. XVHThe Habilitation Thesis of SA?, completed in 1983 at İ.T.Ü. as an extension of his doctoral work completed at 1978 at the Liverpool University has become the basis of internal combustion engine simulation research of İ.T.Ü. This program has been used effectively by various postgraduate researches at İ.T.Ü. after 1983. The research done so for can be summarized under three main headings: Air flow modeling, Combustion and heat transfer in engine cylinders, Overall engine simulation, This thesis work can be classified under the heading“overall engine simulation”. The theory of modeling which forms the basis for the simulation program is based on the assumption that the gas flow in the inlet and exhaust manifolds of the diesel engines progress as time dependent, one dimensional flow with variable entropy among the gas particles. The nonlinear hyperbolic partial differential equations obtained from the equations of continuity, momentum, and general energy are solved by the method of characteristics, also using the theories of boundary conditions. The computer program used [1] has been adapted into FORTRAN 77 language; and is composed of one main program, seven subroutines and 25 secondary subroutines [2]. The simulation programs and data files are given in a floppy disk which is included in Appendix F. A diesel engine can meet the demands of a variable load by increasing or decreasing the fuel injected to the combustion chamber at each cycle. This variation can be achieve either by a speed control lever for the case of a variable speed engine or by a constant speed governor for the case of a constant speed diesel engine. In both cases, the command that is given either by the speed control lever or by the constant speed governor is fed into the fuel injection pump's control rack; whose axial motion is converted to a rotational motion by a control gear inside the pump and vary the effective stroke of the injector's plungers (Figure 5.1). The fuel camshaft of the pump moves the plungers axially, whose effective strokes are thus varied; and therefore, differing amounts of fuel are injected to cylinders for differing load conditions. In order to simulate the above mentioned process numerically, the amount of fuel injected should be altered at the input data file of the program. Since, the variation of the fuel will change the amount of heat released as a result of the combustion process, the pressure and temperature of the exhaust gases will also change. As a result, the energy recovered at the turbine of the turbocharger unit will vary and the pressure and temperature of the air charged into the intake manifold of the engine will change. As a result, the parameters to be charged for a diesel engine to be simulated for variable fuel conditions are specified as; Amount of fuel to be injected to the cylinder for a cycle, Mean pressure of the exhaust manifold, Mean temperature of the exhaust manifold, Mean pressure of the intake manifold, Mean temperature of the intake manifold. XVlllThis research was made on a MTU 16V 396 TB34D diesel engine, which is a stationary generator application of the MTU's 396 TB series. Five different data files for the variable load conditions of the engine are created, based on the information supplied by the manufacturing company's Istanbul branch office. The computer program has first been run for a 100 % load condition. This study was aimed at the converging criteria research of the results by varying the number of the cycles. When the results of effective power, mean effective pressure, specific fuel consumption and thermal efficiency are compared, the second group of results are seen to be approximately equal to the third and fourth group of results (Table 5.2). Therefore, the number of cycles in the program was assumed to be 8 and the second group of solutions obtained were assumed to be the analytic solution. The following graphs were plotted (Appendix C) by using the data in the output files for the 100 % load condition; Variation of pressure during the change of air charge (open cycle), Variation of pressure during compression, combustion and expansion (closed cycle), Variation of pressure on the cylinder-exit edge of the intake manifold, Variation of pressure on the exhaust-manifold entry side of the cylinder, Variation of mass flow rate while the exhaust values are open, Variation of mass flow rate while the intake values are open. The program has been re-run with the values given in Table 5.1 for variable load conditions. The effective power, mean effective pressure, specific fuel consumption and thermal efficiency can be seen in Table 5.3. When the analytical results and the relevant engine test bed results included in the engine protocol (Table 5.4) are compared, the results are seen to be in a good agreement and the performance curves plotted in Figure 5.5 are in the same character. By using the data from the output files for varying load conditions; Closed cycle pressure variations, Pressure variation during the change of charge, Pressure variation at the cylinder entrance edge of the intake manifold, for the B3 cylinder for each load condition have been plotted. Those curves are included in Appendix D. The study made so far has indicated that the above-mentioned simulation program can be effectively used for fixed-revolution diesel engines, generator driver diesel engines and pitch-controlled marine power plants. In the next phase of study, the effects of variable valve timing for engine performance was investigated. By taking the fact that the diesel engine taken into account has originally optimum values of intake and exhaust valve timing, the effects of very minute changes were investigated. Again, in five different load conditions, the program was ran for opening and closing advance and delay cases of 4 degrees and when Table 6.1 was investigated, the following results have been identified; XIXi. Earlier closing of the intake valves has caused a drop in engine performance, ii. Delaying the closing of the intake valves has caused an increase in engine performance. When the load is decreased, the performance was observed to increase, iii. Earlier opening of the intake valves has increased the engine performance for increasing load conditions. But however, earlier opening of the intake valves at low load conditions causes a drop in performance, iv. Delaying the opening of the intake valves causes an increase of performance for low load conditions, but however, a decrease in performance for increasing load conditions, v. Since opening of the intake valves mark the start of the overlap period, it is concluded that the overlap period should be increased to improve the engine performance for increasing load conditions and decreased for decreasing load conditions, vi. Earlier closing of the exhaust valves have not caused an important performance increase. Only a performance increase at 25 % load condition was observed; which was regarded to indicate that the reduction of the overlap period at low loads increase the engine performance, vii. While the delayed closing of the exhaust valves decrease the engine performance for low loads, it has not created an increase in the engine performance with higher load conditions contrary to what was expected, viii. The closing of the exhaust valves mark the end of the overlap period. Extending the overlap period will elongate the scavenging process and increase the inertia of the charge air. This in turn shall extend the swirl motion of the air inside the cylinder and cause an improvement in air-fuel mixing during the injection process. Unfortunately, the program is based on a fixed heat release rate model and the effects of the parameter charges to combustion and the effects of combustion to the engine performance are not observable. Therefore, the effects of delaying the exhaust valves closing could not been investigated. The effects have only been evaluated from the point of view of charge variation, ix. Earlier opening of the exhaust valves have increased the engine performance for increasing loads; but however, caused a decrease of performance for lower load conditions, x. Delaying the closing of the exhaust valves have caused a performance increase for lower load conditions, but a decrease in performance for higher load conditions, xi. While the closing timing of exhaust and inlet valves have different characters, their opening timing has a similar effect. While earlier opening of the intake and exhaust valves cause a performance increase with increasing load conditions, their delayed opening cause a performance increase for lower loads. XXAll those above mentioned results indicate that variable valve timing affects engine performance for variable load conditions. When the charges that increase the engine performance are taken into account, it is concluded that specific fuel consumption can be reduced for variable loads. As it is known universally, variable valve timing (WT) technology has been started to be applied to SI engines by manufacturers like Nissan and Honda. Theoretical studies for WT application for diesel engines are still under progress. The theoretical results obtained as a result of this thesis work can be developed to achieve design changes involving camshafts to vary intake and exhaust valve opening and closing sequences. It is proposed that the camshaft with variable cams on can be moved axially by the commands taken from the diesel engine governor to increase the engine performance. XXI
Benzer Tezler
- Gaz türbinlerinde su/buhar enjeksiyonunun termoekonomik performans ve emisyonlar üzerindeki etkisinin incelenmesi ve optimizasyonu
Effects of water/steam injection on the thermoeconomic performance and emissions of gas turbines and their optimization
HASAN KAYHAN KAYADELEN
Doktora
Türkçe
2014
EnerjiYıldız Teknik ÜniversitesiGemi İnşaatı ve Gemi Makineleri Mühendisliği Ana Bilim Dalı
PROF. DR. YASİN ÜST
- Buji ateşlemeli motorlarda çevrim atlatma yönteminin kısmi yüklerde incelenmesi
Skip cycle method investigation at part load conditions of spark ignition engines
BARIŞ DOĞRU
Doktora
Türkçe
2013
Makine Mühendisliğiİstanbul Teknik ÜniversitesiMakine Mühendisliği Ana Bilim Dalı
YRD. DOÇ. DR. OSMAN AKIN KUTLAR
- Numerical and experimental study of turbulent jet ignition method on wankel engine with passive pre-chamber
Türbülanslı jet tutuşturma yönteminin wankel motorunda pasif ön yanma odası ile numerik ve deneysel çalışması
HARUN DİLLİCE
Yüksek Lisans
İngilizce
2024
Makine Mühendisliğiİstanbul Teknik ÜniversitesiMakine Mühendisliği Ana Bilim Dalı
DOÇ. DR. OSMAN AKIN KUTLAR
- Experimental combustion analysis of diesel engine
Dizel içten yanmalı motorlarda yanmanın deneysel incelenmesi
TOLGAHAN KAYA
Doktora
İngilizce
2019
Makine Mühendisliğiİstanbul Teknik ÜniversitesiMakine Mühendisliği Ana Bilim Dalı
DR. ÖĞR. ÜYESİ OSMAN AKIN KUTLAR
DR. ÖZGÜR OĞUZ TAŞKIRAN
- Zero/one dimensional numerical modelling and effect of variable compression ratio (VCR) on emissions and performance of a four-cylinder turbocharged diesel engine
Dört silindirli turboşarjlı dizel motorun sıfır / bir boyutlu sayısal modelleme ve değişken sıkıştırma oranının (VCR) emisyonları ve performansına etkisi
DANIYAL KHAN
Yüksek Lisans
İngilizce
2019
Makine MühendisliğiMarmara ÜniversitesiMakine Mühendisliği Ana Bilim Dalı
PROF. DR. MEHMET ZAFER GÜL