Darbeli detonasyon motoru (DDM) ile farklı konfigürasyonlarda detonasyon dalgası oluşturma
Creating detonation wave in different configurations with pulsed detonation engine (PDE)
Yazar: ALİ CEM BULUT
Danışman: DR. ÖĞR. ÜYESİ MURAT ÇAKAN ; PROF. DR. ONUR TUNÇER
İstanbul Teknik Üniversitesi / Enerji Enstitüsü / Enerji Bilim ve Teknoloji Ana Bilim Dalı / Enerji Bilim ve Teknoloji Bilim Dalı
Derece: Yüksek Lisans, 2022
Konu: Enerji = Energy ; Havacılık Mühendisliği = Aeronautical Engineering ; Makine Mühendisliği = Mechanical Engineering
Dizin: Detonasyon = Detonation ; Hidrojen = Hydrogen ; Motorlar = Motors ; Oksijen = Oxygen ; Patlama = Explosion ; Roketler = Rockets ; Verim = Yield ; Yanma = Combustion

Özet:
Darbeli patlatma, mevcut motor sistemlerinden daha verimli itki üretmek için yakıtın patlatılmasını içeren bir tahrik teknolojisidir. Teorik araştırma ve deneyler ile, tekno-lojisinin mekanik basitliği, termodinamik verimliliği sayesinde mevcut motor tiple-rinden daha verimli olduğu gösterilmiştir. Darbeli Detonasyon Motoru(DDM), yak-laşık olarak Mach 2.3'e kadar hızlarda karşılaştırılabilir. Ramjet motorlarından daha yüksek bir özgül itme ürettiğinden, çok aşamalı bir tahrik sisteminin parçası olarak kullanım için uygundur. DDM, bir ramjet veya scramjet motor için statik itme sağla-yabilir veya turbofan sistemleriyle birlikte çalışabilir. Bu nedenle, havacılık, uzay ve askeri endüstrilerin birçok sektöründe potansiyel uygulamalarda görülmektedir. Bu-nunla birlikte, DDM'nin pratik kullanımını görebilmesi için üstesinden gelinmesi gereken mühendislik zorlukları vardır. Patlama sürecini başlatmak, sürdürmek ve sürekli kılmak için mevcut yöntemlerin iyileştirilmesi gerekiyor. Bu amaçla, birçok kurum ve kuruluş bu gelişimi sağlamak için farklı süreçler geliştirdi. Farklı yakıt, tasarım, püskürtme, türbülans yöntemleri, patlama bölgesindeki boyutlar ve sıcaklık-lar gibi parametrelerle detonasyon dalgasını sürekli ve sabit kılmak üzerine çalışıyor-lar. Aynı şekilde buradaki araştırma ekibi de bu değişen tasarım kombinasyonlarını bizzat yerinde deneyerek aynı çalıştaya katkı yapmayı hedefliyor. Detonasyon dalga-sını üretmek ve stabil kılmak için en uygun tasarımı ve parametreleri bulmak için gereken deneysel çalışmaları yapıldı. Sonuç olarak, çoğu test vakasında arka çekir-dek-gövde basıncı bilinmiyordu. Basınç ölçümünün belirsizliğine teorik olarak kavi-tasyon ve keskin kenar yaklaşımı ile yaklaşılsa da enerji kaybı ve farklı hızlarda ve sıcaklıklarda hazne dolumu gibi değişkenler nedeniyle farklı belirsizliklerle basınç ölçümüne neden olabilirdi. Enjektörlerde oluşan basınç ve enerji kayıpları ve enjek-tördeki yakıtın homojenliği tam olarak bilinmemektedir. Normal tasarım koşulları, 350 -500 mm boru boyları, 200 mm yay uzunluğu, 10, 20,25 mm yay adımları, 2, 2,5 yay tel kalınlıkları, farklı aralık tasarımları ve farklı aralık mesafelerine sahip dik-dörtgen 4 veya 5 engel, 2- 5 mm^2 dikdörtgen geçiş alanları, 0-200 °C sıcaklık fark-ları, farklı püskürtme stilleri ve ince delikli ve araç enjektörleri gibi farklı enjektör tasarımları, hidrojen ve kerosen gibi farklı yakıt kullanımı, farklı basınç sensörü ko-numlandırma, 0,5-3 stokiyometrik oranlarda, 1 - 12 bar basınçlı yakıt ve oksitleyici, 0 - 5 sn tutuşma süreleri arasında farklı kombinasyonlar üretilerek testler yapılmıştır. Patlama dalgası oluşumu 350 mm uzunluğunda, 10 mm çapında, 1/3 parçada 2 mm et kalınlığında, 10 mm hatve yayı geometrik koşullarında, oda sıcaklığında, stokiyo-metrik oran 1.1, 5 g/s hidrojen ve 40 g/s'de en güçlüdür. s Akış hızlarında ateşlenerek oksijen gazı elde edilmiştir. Güçlü patlama dalgaları olarak değerlendirilen sonuçlar-da 14 bar basınç ve 3266 m/s hız elde edilmiştir. CEA sonuçlarıyla karşılaştırıldığın-

Abstract:
Pulse Detonation is a propulsion technology that involves blasting fuel to produce thrust more efficiently than existing engine systems. With theoretical research and experiments, it has been shown that the technology is more efficient than existing engine types such as ramjet, scramjet, turbofan. Thanks to its mechanical simplicity and thermodynamic efficiency. The pulsed detonation engine emerges as a potential tool that can enable the oxidizer and fuel mixture to burn in chemically better condi-tions. Compared to the currently used gas turbine engines, it creates a much more efficient combustion and explosion in much less entropy. The basis of this process is pressure gain and sudden temperature peaks and the work that can be gained from this temperature difference. Since the loss in entropy is reduced, the resulting chemi-cal cycle is more efficient and more purposeful.
PDE is comparable in speeds up to approximately Mach 2.3. It is suitable for use as part of a multistage propulsion system as it produces a higher specific thrust than ramjet engines. PDE can provide static thrust for a ramjet or scramjet engine or work in conjunction with turbofan systems. Therefore, it is seen in potential applications in many sectors of the aerospace, space, and military industries. Since the system crea-ted in theory can be implemented in practice, many institutions and organizations around the world want to be a part of this process, researching and developing it clo-sely. However, there are engineering challenges to overcome before PDE can see practical use. Existing methods need to be improved to initiate, maintain and perpe-tuate the explosion process. For this purpose, many institutions and organizations have developed different processes to achieve this development. They work on kee-ping the detonation wave continuous and constant with parameters such as different fuel, design, injection, turbulence methods, dimensions, and temperatures in the de-tonation zone. Likewise, the research team here aims to contribute to the same workshop by trying these changing design combinations on site.
Experimental work was done to find the optimal design and parameters to generate and stabilize the detonation wave. The baseline study performed shows that the tes-ted parameters, the obstacle ratio, the number of obstacles, and the distance between the obstacles are all statistically significant. PDE section length and spacing are the most important, followed by the barrier ratio. All two-way interactions, except the interaction of the blocking rate with the cavity, the significant pulse flame velocity. Increasing blockage rate, number of obstacles, and spacing (within the design area under consideration) will accelerate the flame faster within the tested limits. It has been shown that for a given fuel, the DDT(deflegation to detonation transition) boom cross-section length has the greatest influence on the detonation initiation behavior, followed by the distance between the obstacles along the tube. This data collection process is recommended for shaping and acquiring data for DDT in a round-sectiontube for future single-shot or low-frequency low-duration experiments where the burst transition location is desired.
It was seen that kerosene needs much more time to detonate than hydrogen, that is, it is quite difficult to burn compared to hydrogen. This trend would likely continue as heavier/less sensitive hydrocarbons were used. The longer PDE section was an im-portant factor for the transition to detonation and the formation of detonation. It has been observed that the fuel temperature has a positive effect on the explosion. Hea-ting has met the initial energy supply situation in liquid fuel to a large extent. It has been observed that the injector type can again achieve better results in the explosion and facilitate combustion. It was discovered that the bow and its derivatives can tur-bulence better than the direct obstacle. Optimizing the barrier was quite difficult. Because it obstructed its passage as much as it was turbulent the flow.
The final design was created by looking at all these parameters, and firing the hydro-gen directly with oxygen was determined as the best design option to create the most efficient detonation wave. Precise measurements were important given the interest in measuring PDE performance and (where possible) validating the benefits from the detonation process. Therefore, many various sources of uncertainty have been consi-dered throughout the experimental process and post-processing. In general, certain areas of uncertainty fall into three broad categories; measurement uncertainties. The-se uncertainties were often directly associated with the measurements, instruments, and data system. Therefore, they could be easily measured, system transients. Becau-se the RDE never reached a true steady-state operating condition during testing, tran-sients remaining within the data windows used to measure meta-steady-state perfor-mance introduced additional uncertainty. These uncertainties are generally calculated using traditional standard deviation metrics associated with the data points collected, other uncertainties. Many uncertainties regarding hardware or system operation were considered insignificant, difficult to measure, or both. For this reason, they are dis-cussed but not included in the official uncertainty analysis. The measurement uncer-tainty of the daq system used for the cysts pressure sensor is around 0.5%. Line pres-sure sensor reading uncertainty is in the order of -+ 0.3. Gas purity rates are 99.5% and above. Cavitation and sharp edge pressure loss values are used in the platform pressure calculation. Values leading to cavitation, energy, and pressure loss were calculated. Many uncertainties associated with the engine testing process were consi-dered minimal, difficult to measure, or both. As a result, they were not included in the formal uncertainty analysis method discussed above or in the imprecise bounds subsequently provided for each data point. Some specific areas of uncertainty that are excluded from this process are as follows: Platform wall heat loss It is likely that heat loss from the chamber wall will lower the gas temperature and consequently the po-tential chamber pressure by 1-2%. However, since the heat flow estimation is based on extremely limited data, the effect of heat loss on chamber pressure cannot be es-timated more accurately than this. Stabilization of aft core-stem pressure. The stern center-to-body pressure gauge seldom stabilized during operation without the nozzle attached, and generally did not record significant data in most tests. As a result, in most test cases, the posterior core-stem pressure was unknown. Although the uncer-tainty of pressure measurement is theoretically approached with the cavitation and sharp-edge approach, it can cause pressure measurement with different uncertainties due to energy loss and variables such as chamber filling at different speeds and tem-peratures. In injectors. The pressure and energy losses that occur and the homogene-ity of the fuel in the injector are not known exactly. Normal design conditions, tube lengths between 350 -500 mm, spring length of 200 mm, spring steps of 10, 20,25 mm, spring wire thicknesses of 2, 2.5, rectangular 4 or 5 obstacles with different spa-cing designs and different spacing distances, 2- 5 mm^2 rectangular transition areas, 0-200 °C temperature differences, different spray styles and different injector designs such as fine-bore and vehicle injectors, different fuel use such as hydrogen and kero-sene, different pressure sensor positioning, 0.5-3 stoichiometric ratios, tests were carried out by producing different combinations between 1 - 12 bar pressurized fuel and oxidizer, 0 - 5 sec ignition times. Results and comparisons are presented. Deto-nation wave formation is strongest at 350 mm length, 10 mm diameter, 2 mm wall thickness in 1/3 part, 10 mm pitch arc geometric conditions, at room temperature, stoichiometric ratio 1.1, 5 g/s hydrogen and 40 g/s Oxygen gas was obtained by fi-ring at flow rates. Pressure at 14 bars and a speed of 3266 m/s were obtained in the results, which were evaluated as strong detonation waves. Hydrogen-oxygen was classified as a strong detonation wave when compared to CEA results.