44nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit AIAA 2008-4780 20-23 July 2008, Hartford, Connecticut, USA

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Overview of Current Activities on PDE and Pulse Detonation Propulsion in China

Hao TANG1, Yue HUANG2 Nanjing University of Aeronautics and Astronautics, Nanjing, China, 210016

Hong LIU3 Jiangsu Polytechnic University, Changzhou, China, 213016

and

Jia-Hua WANG4, Minxiang WEI5 Nanjing University of Aeronautics and Astronautics, Nanjing, China, 210016

This paper reviews current activities in the development of pulse detonation engines (PDE) and pulse detonation propulsion in China. During the past 10 years or so, there have been continued PDE and pulse detonation propulsion research toward developing practical power and detonation-driven propulsion systems. Recent progress includes numerical and experimental investigation on two-phase Detonation, multi-cycle and multi-tube PDE. The current PDE activities mainly in a leading academic groups - NUAA are briefly presented.

Nomenclature NUAA = Nanjing University of Aeronautics and Astronautics NWPU = Northwestern Polytechnical University USTC = University of Science and Technology of China IMECH = Institute of Mechanics, Chinese Academy of Sciences PDE = Pulsed Detonation Engine DDT = Deflagration-to-Detonation Transition RVPDE = Rotary-Valved Pulsed Detonation Engine PDRE = Pulsed Detonation Rocket Engine CNKI = China National Knowledge Infrastructure U = velocity X = distance T = time F = Instantaneous thrust

I. Introduction HE potential for PDE air-breathing operation is highly attractive from the perspectives of efficiency and operation1. In recent years propulsion systems based on PDE have received increased attention in most

western countries. Continuing high costs and growing envirmental pressures also could inject new urgency into development of PDE technology for wider commercial applications, rather than just military2.Recent developments in the research on pulse detonation engines are revealed and published by developed countries，such as several programs sponsored by ONR, Air Force, NASA, DARPA in the USA as well as several parallel efforts in Belarus, Canada, Japan, Russia, Sweden and other countries3. However, currently efforts made in China just have a relatively short history; research on PDE has just been conducted mainly by these academic

T

1Professor, Institute of Pulse Detonation Engine, College of Energy and Power Engineering, 29 Yudao Street. Nanjing, hao.tang@nuaa.edu.cn, 2PhD student, Institute of Pulse Detonation Engine, College of Energy and Power Engineering, 29 Yudao Street. Nanjing,China 3Lecture/PhD candidate,. Department of Mechanical Engineering, Changzhou, China 4Professor, honorary director, Institute of Pulse Detonation Engine, College of Energy and Power Engineering, 29 Yudao Street. Nanjing, China 5Professor, head, Dept. of Vehicle Engineering, College of Energy and Power Engineering, 29 Yudao Street. Nanjing, China

44th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit21 - 23 July 2008, Hartford, CT

AIAA 2008-4780

Copyright © 2008 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

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groups: NUAA, NWPU, IMECH, USTC, etc. Figure1, Figure 2 and Figure 3 shown the statistic of publications related pulse detonation, these based on CNKI database. While an attempt is made to cover a broad range of reported research, actually it is impractical to be exhaustive. Rather than providing a chronological report within a decade, an attempt is made here to discuss the recent progress in terms of broad topic areas.

The present paper reports the recent 10 years PDE research in China by NUAA and other academic groups.

NUAA PDE group conducted experimental and numerical studies on PDE or PDE-related in the following aspects: detonation wave formation mechanism and structure, detonation initiation, mechanism of two-phase detonation combustion, self-fit control of fuel injection system, net thrust estimates, numerical investigation on 2D detonation wave，study on PDE-related components , key technology of small size PDE and PDTE4-12. NWPU PDE group performed thermodynamic cycle analysis and performance estimation of PDE prototype, experimental studies on two-phase PDE and PDRE, numerical investigation on gaseous phase and two-phase detonation wave and exploratory research on simulated launch regarding pulse detonation engine,etc13-19. IMECH developed a series of numerical study on detonation wave formation and propagation, experimental studies on pulse detonation propulsion system, fuel injection and mixing and mechanism of PDE cycle, etc20-

21.USTC did a lot of work on numerical studies on detonation wave and experiment study on detonation wave diffraction with double exposure holographic interferometric measurement and detonation wave propagation through a T-shape bifurcated tube22-24. Besides, Some other academic groups engaged in PDE study25-29.

II. Theoretical Analysis Study on fundamental mechanism of detonation is crossed over propulsion and an explosion area, the later is

in advance to researchers of PDE and benefit to understanding fundamental theory of pulse detonation propulsion. There are two text books published for students in area of explosion and propulsion on detonation topic27, 28. Although fundamental detonation research has been performed for a long time in China, the PDE-related studies have a relatively short history. Now, some academic groups in explosion area also begin to take part in PDE research25, 26, it will promote the development of detonation in PDE propulsion and make propulsion specialist more deeply understand detonation characteristic.

Based on the working principle and operating cycle process of PDE or simplified gasdynamic analysis, some analytical models for the performance of a single-cycle idealized pulse detonation engine are established. The Performance of PDE was theoretically analyzed by using these models5, 12, 19. The thermodynamic performance of a partially-filled PDE is also analyzed by ref.[19]. All of these analysises have confirmed the thermodynamic

Pubications

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Figure 1. Schematics of increasing trend on publications based on CNKI

Pulse Detonation

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Figure 3. Categorized percentage of journal papers

Pulse Detonation

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Figure 2. Categorized statistics of journal papers

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performance of PDE cycle, compared to Brayton and Humphrey cycle over some parameters (filling or flighting mach number, compression ratio, the mass ratio of residual purge fluid to detonation fluid, etc). The advantage of the PDE cycle is significantly5,19. However, due to a large of losses in the actual operation process, it has been difficult to these superior thermodynamic efficiencies to transformed propulsive performance29. Further study has been done to validate these analysises with experiential data and numerical computation , at the same time the total pressure loss was taken into account12.

III. Experimental approach Much effort has been expended in studying various important aspects and components of PDE

experimentally. These studies can be divided into single-pulse and multicycle, single-tube and multi-tube, gaseous and two-phase, valveless and rotary-valved PDE experiments. Single-pulse experiments can be used to measure the detonation wave properties, and to investigate DDT process11.multicycle experiments focus on achieving high-frequency-operation since the PDE concept was presented, In order to obtain quasi-steady thrust and increase thrust-to-weight ratio8, multi-tube experiments can be used to explore the feasibility of PDTE4. Now, the hot topic of experimental studies are two-phase detonation initiation and properties, mixing and atomization of liquid-fuel, high-frequency-operation, adaptive control of detonation, pre-detonator, PDTE, PDRE and Simulated Launch13.

In the two-phase detonation studies, NUAA and NWPU group both have done a lot of excellent work. Figure 4 is two-phase aero-valve PDE experimental setup of NUAA. NWPU specialized two-phase PDRE, and achieved many research results. NUAA was good at PDTE and large-scale PDE studies. However, Previous studies may focus on detonation tubes, it is very difficult in practical application. So, scientists here have been aware of the problem and begin exploratory research13.

IV. Numerical Studies Numerical investigations on detonation formation, propagation, diffraction and reflection have been

performed using gaseous detonation CFD code for a long time. As PDE studies carried out in China, researchers began to apply original gaseous detonation code to PDE work process. The numerical studies of PDE mainly focused on 1D and 2D, and there was almost no 3D numerical investigation. The method of detonation initiation mainly used an initial high pressure and temperature region of reactants at one-end of the closed tube without considered DDT, most numerical studies use hydrogen (H2) as the fuel because of its relatively simpler chemical kinetics. However, numerical study on DDT process has aroused extensive attention. Now, NUAA and NWPU group both have been carried out numerical investigations on DDT process (Figure 5)6, 16. Besides, much effort was expended to numerical analysis the effect of nozzle configuration on the PDE performance5,

22, 23, 25. There has also been a lot of work on numerical

simulation of two-phase detonation wave16, 26. The nonlinear instability of one-dimensional detonation wave was numerical simulated in the mixture of gas hydrocarbon with air26. Mechanism of DDT of liquid octane/air mixture is studied by using the theory of one-dimension reaction flow, particle-trajectory model and two-step reaction model. The generation, evolution,

Figure 4. Schematic of two-phase aero-valve PDE setup8

Figure 5. Characteristic of shock-flame interactions6

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propagation and basic properties of liquid-fueled detonation structure were investigated.16 In addition, because of the lack of the DDT and high accuracy numerical scheme, the results have certain

limitations. In spite of many simplifications used in the numerical simulation, it still plays an important role in understanding of the characteristics of detonation propagation in combustor, and gives some guiding roles to experimental studies.

V. Current activities Current activities discussed in this section is mainly focused on authors group, as a leading research group

on air-breathing pulse detonation engine, pioneered achievements include experiment of two-phase PDE, small-scaled PDE, pre-detonator, adaptive control & diagnostics, new performance evaluation method-PLCM model，novel structure for shorten DDT and enhancement of mixing etc..

Reliable and repeated low-energy initiation of detonations in the high-speed flow in pulse detonation

engines operating on practical mixtures is one of the most challenging problems in the development of these engines29. Much research efforts have been done on this topic. Several kinds of obstacles including, Shchelkin spirals, semi-V, V and annular type.etc to enhance combustion were designed4, 9, 10(as shown in Figure 6). Various types of detonator were designed to improve fuel vaporization and detonation initiation, shown in Figure 7.

In order to obtain quasi-steady thrust and increase thrust-to-weight ratio, we conducted research work about improving the frequency of PDE.Figure 8 shown a two-phase highly frequency aero-valve PDE prototype, it can steadily and periodically operate at the frequency of 50Hz.

Based on the investigation of the key technology including aero-valve, integration design of aero-valve and atomizer, the fuel vaporization and mixing, the improvement about ignition reliability and intensification of burning, a pulse detonation rocket engine prototype is designed, the diameter and the length of the engine are 58 mm and 1300 mm,Using the gasoline/air as the propellant. Figure 9 show test rig of PDRE installed on a trolley, can steadily and periodically operate at the frequencies of 25～40Hz.

In order to explore the feasibility of PDTE, a PDE consisting of multiple tubes operating at different

phases was established. Recently, our group performed micro-PDE experiments for the concept of small-scale thruster. Much effort has been expended in studying various important aspects of PDE experimentally in our group, these studies are briefly summarized in Table 1.

Figure 6. Schematic of the obstacle configuration4,

10, 11

Figure 7. Schematic of the vaporized-detonator4, 9

Figure 8. Prototype of two phase PDE with aero

valve7

Figure 9. Test rig of PDRE installed on a trolley8

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Table1 Brief summery of experimental investigations of PDE by NUAA

Propellants Tube diameter D(mm)

Tube lengthL(m)

DDT Augmentation

Frequencyf(Hz) Research focus

Kerosene/air 15-29 1 Shchelkin spiral 30 Small-scaled PDE C2H2,C3H8/O2 20~60 1 turbulence strip single-pulse Detonation Initiation Gasoline/air 58 1.275 turbulence generator 50 High frequency and PDREGasoline/air 80 1.2 detonator 20 triple-tube RVPDE

Kerosene/air 100 1.3-2.4 Detonator, dual semi-V 30 multi-tube aero-valve PDE

Gasoline/air 180,210 2.5-4 Semi-V, annular and plus radial type 15 Valveless large-scale PDE

Numerical simulations based on upwind total-

variation-diminishing (TVD) scheme are carried out for single-pulse PDE with different nozzles. The flow evolutions of different nozzles during a full cycle are investigated, much effort was expended to analysis the effect of nozzle configuration on the system performance. The flow field interaction among detonation tubes sharing a common nozzle in a multi-tube PDE is explored5. Figure 10 shows the thrust wall force for the all configurations nozzles, nozzles affect the chamber flow dynamics significantly and change performance through modification of the gas expansion process.

VI. Concluding remarks The activities and progress of PDE studies in

China has been presented. Fundamental research and exploratory development initiatives ware pursued to understand the detonation physics involved with initiating and controlling detonations, related experiment and measurement means were established. At the same time, the associated in-depth numerical studies were also carried out. To develop and demonstrate PDE and pulse detonation propulsion, there were a lot of experimental and numerical studies in two leading groups, some usefully key technologies of PDE were achieved.

The basic ideas behind most of the current PDE systems being investigated have been known for a while, but still the detonation phenomenon-the kernel of the PDE operation need to be understood. Further research is evidently needed to make practical propulsion devices based on detonation waves a reality. The follow PDE-related technology research should be strengthened, such as: atomizers for generating very fine droplets and techniques for mixing enhancement, controlled the evacuation of exhaust gases, inlet and nozzle , practical PDE performance, in order to acquire high frequency and multi-tube successfully operation.etc. The heat transfer and noise from PDEs have also not been reported in any detail, this topic also Should be made some effort.

Nevertheless, researchers have shown enthusiasm in research and have achieved usefully key technologies. The results that have been obtained so far give all reason to be optimistic. In order to overcome wider range of problems that researcher encounter in further, to solve basic problems necessary to design applied PDE and pulse detonation propulsion, better understand detonation phenomenon , strengthened tests measuring equipment, etc are required, multidisciplinary and multi field cooperation efforts should be made.

Acknowledgments This work was supported by the National Natural Science Foundation of China (50776045).

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cases. Stoichiometric H2/Air; p0 = 1.0 bar; T0 = 300 K; D-diveging, C-converging, CD-converging -diverging 5.

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