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Yan S.,Liquid Engines | Li B.,Liquid Engines | Li B.-C.,Liquid Engines | Li F.,Liquid Engines
Yuhang Xuebao/Journal of Astronautics | Year: 2017

There are some problems with the traditional modal test method by pasting vibration sensors, such as influences of additional sensor mass, low mode shape resolution, etc. In order to solve these problems, 3-D scanning measuring technique based on laser Doppler vibrometry and robot platform are studied. Taking the case of liquid rocket engine (LRE) combustion chamber and oxidant entrance pipe, modal tests based on 3-D scanning measuring technique are carried out and high spatial resolution mode shapes are obtained. The effect of the additional mass of the sensors on the pipe modal test results is analyzed quantitatively. The results show that 3-D scanning measuring method has the advantage of high precision, fast test speed, and unlimited number of measuring points, etc. © 2017, Editorial Dept. of JA. All right reserved.

Yan S.,Liquid Engines | Li B.,Liquid Engines | Li F.,Liquid Engines
Proceedings of the International Astronautical Congress, IAC | Year: 2016

Accurate calculation of dynamic loads during steady operation of liquid rocket engine(LRE) is of great importance to the engine design. However, self-induced mechanical loads at the combustion chamber and turbopump can't be directly measured. A general identification method is through the acceleration response near the excitation sources and frequency response function(FRF) matrices obtained by testing or the finite element model. Unfortunately, multi-sources load identification problems are generally illposed. High condition number of FRF matrix will cause enormous error in the identification result. Aim of this paper was to validate the load identification technique on the rocket engine and Tikhonov regularization was carried out to stabilize the solution. The response cross power matrices were restructured by the proper orthogonal decomposition(POD) technique. Strategies to improve the identification result, weighting matrix and selecting the measurement points according to the condition number of FRF matrices, were adopted. Dynamic load identification experiment was performed on a second stage liquid rocket engine, which was tested with known force inputs from shakers attached to three well defined locations. Results showed that the random and sinusoidal dynamic loads were identified simultaneously with a satisfactory accuracy. Copyright © 2016 by the International Astronautical Federation (IAF). All rights reserved.

Yan S.,Liquid Engines | Li B.,Liquid Engines | Li F.,Liquid Engines | Yang Q.,Liquid Engines
Proceedings of the International Astronautical Congress, IAC | Year: 2016

The 18,000-kg thrust staged combustion cycle LOX/Kerosene engine has been successfully developed at Xi'an Aerospace Propulsion Institute. As a second stage engine of china's new generation launch vehicle, it is suffered from vibration loads transmitted through the vehicle during steady state operation of the first stage engine. So the structural dynamic characteristics of engine determine its structural integrity. The engine frame was modified to improve its structural dynamic characteristics during the design process. A modal test was carried out and modal parameters including natural frequencies, mode shapes less than 200Hz were obtained. A finite element model of the engine consisting of nozzle, combustion chamber, turbopump, etc was developed. Hard work was made to tune the finite element model according to test results and the detailed simplified methods were described. After the single engine model was established, the finite element model of four parallel connected engines, used for the second stage of new generation medium-sized rocket launch vehicle, was built up. The effectiveness of the model was also validated by the four parallel connected engines modal test. Copyright © 2016 by the International Astronautical Federation (IAF). All rights reserved.

Cherian S.A.,Liquid Engines | Arun Kumar P.,Liquid Engines | Rajeev Senan C.,Liquid Engines | Ajith B.,Liquid Engines
Proceedings of the International Astronautical Congress, IAC | Year: 2016

The 440N bipropellant Liquid Apogee Motor (LAM) is used for orbit raising of satellites from Geostationary Transfer Orbit to Geostationary Orbit. Liquid Propulsion Systems Centre(LPSC) of Indian Space Research Organisation(ISRO) has developed and qualified LAM and it was successfully used in thirty four spacecraft missions including Chandrayaan-1, the mission to moon and in Mangalyaan, the mission to Mars. The propellant combination employed is MON-3 MMH at a mixture ratio of 1.6. The engine with an area ratio(AR) of 160 delivers a thrust of 440 N with a specific impulse(ISP) of 315 s(nominal) which is the maximum reported in the international scenario for this class of engines having identical AR. LAM uses a single element coaxial swirl injector made of Titanium alloy. The thrust chamber is made of columbium alloy, silicide coated and radiation cooled and it is electron beam welded to the injector. Flow control valves used are of solenoid type with sliding plunger. The valves are assembled to the engine mechanically using two seals. ISRO is venturing to launch heavier satellites in near future and LPSC has undertaken a programme to develop an engine with improved performance. Towards this, a modified version of LAM with enhanced AR is designed. AR is enhanced from 160 to 250 to improve the ISP by over 1% which will result in a propellant saving thus extending the satellite life. The injector configuration remains the same as that of the existing LAM and the nozzle is redesigned for enhanced AR to achieve a higher thrust amplification factor. Two engines were realised and subjected to qualification level vibration and thermo vacuum tests. After this, the engines were subjected to qualification hot tests in high altitude facility. Both the engines showed a gain in ISP of over 1% with respect to nozzle with AR 160 thus validating the design modification. The engines were subjected to off nominal tests also and this version engine will be inducted to Geostationary Spacecrafts soon. This paper presents the details of the qualification tests carried out.

Varghese A.,Storable Upper Stage Group | Mahesh G.,Liquid Engines | Prakash M.N.,Liquid Engines | Manu Mohan M.,Storable Upper Stage Group
Proceedings of the International Astronautical Congress, IAC | Year: 2016

The advantage of liquid rocket engine is its multi start capability for optimising the required injection velocity of the payload. Restarting of liquid stages in space flight enables injecting satellites in different orbits / inclination, payload improvement for mission specific elliptical orbit with greater argument of perigee. Restarting will also help in deorbiting of spent stages and consuming the left out propellants in stages. This will help in reducing the risks of stage explosions and minimizing space debris. Liquid rocket thrusters have undergone restarts earlier in spacecrafts for orbit raising and 3 axis control as well as station keeping. For the first time in Indian launch vehicle program, restart of upper stage pressure fed engines was experimented in one of the recent flights. The restart of engine calls for challenges viz firing the engine in heated condition, purging the engine after hot burn and fixing the idle time between hot starts etc. Mission planning and controllability of the stage were addressed in order to have a smooth restart operation in space. This includes collision free restart, adequate battery power and tracking visibility of the stage. Technical solutions were adopted in propellant management for different fill fractions to settle them at the outlet of the tanks for smooth restart. Ensuring gas free propellants at the outlet of the tank in zero gravity, adequate gas availability for commanding valves and regulators benign thermal condition for the free flow of the propellants are some of the complex propulsion aspects considered in restart mission. Before attempting the restart in flight, ground hot test in simulated vacuum was successfully carried out with 2 restarts to demonstrate the restart capability of the upper stage engine. As part of sequence finalisation for ground tests, engine skin temperature measured in earlier missions were used. The temperature at the time of restart was predicted using mathematical models. Performance of engines during restart in flight was normal and both the engines showed identical behaviour during transients and steady state. The demonstration trials carried out in flight has given sufficient confidence in taking up future restart mission requirements. The details of the restart during flight on upper stage engines and the challenges in stage propulsion system for restart and how it was overcome are elaborated in this paper. Copyright © 2016 by the International Astronautical Federation (IAF). All rights reserved.

Xu Y.-F.,Xian Aerospace Propulsion Institute | Xu Y.-F.,Liquid Engines | Chen P.-F.,Xian Aerospace Propulsion Institute | Chen P.-F.,Liquid Engines | And 5 more authors.
Yuhang Xuebao/Journal of Astronautics | Year: 2015

To improve the stability of mono-dispersed droplets generated by droplet generator, the dynamic characteristics of droplet generation process are studied. Considering the dynamic characteristics of droplet generator, the combined dynamics model is set up based on the conventional capillary instability theory. The transfer functions and the transfer matrices are deduced. The influence of parameters such as Re number and We number on the growth rate of fluid disturbance are analyzed. The effect of injector length/diameter ratio on the dynamic characteristics of droplet generation process is also discussed. Propanediol used as working fluid is calculated and verified experimentally. The results show that the optimum non-dimensional wave number offsets over 6% for the generated velocity of droplets exceeding 19 m/s, when the dynamic characteristics of droplet generator are considered in the model. And the optimum non-dimensional wave number offsets almost 10% at the rated condition with 30 m/s, so the dynamic characteristics of droplet generator cannot be ignored in this case. © 2015, Editorial Dept. of JA. All right reserved.

Fu P.,Liquid Engines | Lei F.,China Aerospace Science and Technology Corporation | Chen J.,Liquid Engines | Hang Z.,Liquid Engines | Zhao J.,Liquid Engines
Proceedings of the International Astronautical Congress, IAC | Year: 2015

The High thrust LOX/Kerosene Engine, which is called YF-100, is the newly developed oxidizer-rich staged combustion cycle engine for the new generation Launch Vehicles. It is essential to improve structural dynamics characteristics of the rocket engine owing to the significant effects on the structural reliability and thrust vector control of the whole vehicle. Firstly, the structural dynamics simulation model of the rocket engine are given, which consists of thrust frame, gimbal, combustion chamber, nozzle, turbopump and ducts etc. Next, the natural frequencies and mode shapes of the engine system is investigated by finite element analysis (FEA) method, and the accuracy and reliability of simulation model and FEA method is verified through comparison with the results of the modal tests. Furthermore, by developing parametric sensitivity analysis of the finite element model, the effects of different components or parameters on the structural dynamics characteristics of the rocket engine is discussed. Finally, according to the parametric sensitivity analysis results, die modification measurements of the low frequency of the rocket engine are given, which also have been validated by the related modal tests. Copyright © 2015 by the International Astronautical Federation. All rights reserved.

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