Yeoung-Min Han

Effects of Injector Recess and Chamber Pressure on Combustion Characteristics of Liquid–Liquid Swirl Coaxial Injectors

Combustion characteristics such as combustion performance and combustion stability have been studied experimentally using a small liquid rocket thrust chamber with 19 liquid–liquid swirl coaxial injectors. Data were obtained from static pressure, temperature, and dynamic pressure sensors installed in propellant manifolds and the combustion chamber. While changing the recess length of the injector, characteristic velocity and pressure fluctuation data were collected and analyzed. In addition, chamber pressure was varied between 42 and 54 bar, which covers the sub- and supercritical pressures of oxygen. The results show that the longer recess length generally promotes combustion performance and the spray interaction between injectors in the multielement combustor increases the characteristic velocity. When the chamber pressure is above the critical pressure of oxygen, the recess length scarcely affects the pressure fluctuation. However, when the chamber pressure is below the critical pressure, the shift from external mixing to internal mixing of oxidizer and fuel sheets by the variation of recess length significantly degrades combustion stability and induces strong low-frequency instability. Accordingly, the effects of both recess length and operating chamber pressure must be taken into consideration when designing liquid–liquid swirl coaxial injectors.

Effects of Recess Length on Discharge Coefficients of Swirl Coaxial Injectors

An experimental study has been performed to investigate the effects of the recess length on the discharge coefficients of swirl coaxial injectors. Liquid oxygen and kerosene (Jet A-1) were burned in a range of mixture ratios (1.97–3.31) and chamber pressures (43–80 bar) in small liquid rocket thrust chambers. Each thrust chamber was equipped with 19 liquid–liquid swirl coaxial injectors. While changing the recess length of the injectors, static pressure, temperature, and flow rate data were collected and analyzed to calculate the discharge coefficient. The discharge coefficients obtained from hot-firing tests are compared with those from cold-flow tests. Operating conditions such as oxidizer-to-fuel mixture ratio and chamber pressure have some influence on the discharge coefficients. The recess length of the injectors significantly affects the discharge coefficients in the hot-firing tests, but not in the cold-flow tests. The results show that the longer recess length gradually reduces the discharge coefficients. Especially when the liquid oxygen film collides with the kerosene film inside the fuel nozzle, the discharge coefficients of the outer fuel-side injectors decrease more remarkably than those of the inner oxidizer-side. It is thought that the flame anchored inside the recessed region in the swirl coaxial injector confines propellant flows, and the internal mixing of propellants strongly disturbs the outer fuel flow. Since the discharge coefficient is directly related to the injection pressure drop, the effects of recess length on discharge coefficients must be carefully considered when designing liquid–liquid swirl coaxial injectors.

Combustion Stability Assessment of Double Swirl Coaxial Injectors Using Simulant Propellants

*This study is related to conduct model combustion tests applying various double swirl coaxial injectors to identify their combustion stability characteristics. Gaseous oxygen and mixture gas of methane and propane have been used as simulant propellants. A model combustion chamber was designed for its first tangential frequency to be corresponded to that of a full-scale thrust chamber. They were manufactured four different kinds of injector heads with five elements to examine their stability characteristics. The main idea of the experiment is that a propellant mixing mechanism is considered as a dominant factor significantly affecting combustion stability in the full-scale thrust chamber. Self-excited dynamic pressure measurements in the model combustion chamber show different combustion stability characteristics with respect to a recess length of an oxidizer post. The test result shows that the coupling between combustion phenomena and the 1T frequency in the model combustion chamber becomes strengthened according to the increase of a recess ratio.

Construction and Validation Test of Turbopump Real-propellant Test Facility

ABSTRACT Liquid rocket engines of KSLV-II employ a turbopump feed system for propellants. A turbopump real-propellant test facility based on liquid oxygen and kerose ne has been constructed for the experimental verification of the turbopump performance using the real media of propellants(i.e., LOX/Kerosene). The verification tests of sub-systems were perfo rmed such as LOX/kerosene feed system and alcohol burner system. Finally, the performance of t he whole system was executed and verified through a sets of validation tests with the developmen t model of the KSLV-II turbopumps. It has been confirmed that the test facility satisfies the operating conditions and time of the turbopump at the design and off-design performance test using real-propellant.초 록 한국형발사체를 위한 액체로켓엔진은 터보펌프 추진제 공급방식의 시스템으로 이루어진다. 이 터보펌프의 실추진제를 사용하는 실험적 성능검증을 위해 액체산소와 케로신을 토대로 한 터보펌프 실매질 시험설비가 구축되어 왔다. 산화제/케로신 공급 시스템과 알코올버너 시스템과 같은 주요 서브시스템에 대한 검증시험이 이루어 졌고, 터보펌프 개발모델을 이용한 인증시험을 통해 전체 시험설비에 대한 성능검증이 이루어 졌다. 설계점 및 탈설계점을 포함한 터보펌프의 모든 운용조건과 운용시간에 대한 실매질 성능검증시험을 본 시험설비를 이용하여 수행할 수 있는 것으로 확인되었다.Key Words:Turbopump(터보펌프), Real-propellant Test Facility(실매질 시험설비), Liquid Oxygen(액체산소), Kerosene(케로신), Alcohol Burner(알코올버너)Received 22 December 2014 / Revised 12 June 2015 / Accepted 19 June 2015

Development Test of Alcohol Burner for Turbopump Real-propellant Test Facility

ABSTRACT A turbopump real-propellant test facility(TPTF) is to verify the performance of a turbopump unit(TPU) based on liquid oxygen and kerosene. One of the most important sub-facilities is a hot-gas generation system which makes the driving force of the TPU with an alcohol burner. The alcohol burner generates the required flow rates and temperature at the facility using high pressure air and ethanol. In the study, the verification tests of the alcohol burner which was manufactured entirely with domestic technology were performed and fabrication technique and operation skill for the burner could be obtained ahead of the construction of the facility. Two burners will be operated simultaneously for the real-propellant test of 75tf class turbopump and satisfy the power requirement from the turbine of the TPU.초 록 터보펌프 실매질 시험설비는 액체산소와 케로신을 토대로 터보펌프 조립체의 성능을 검증하는 시험설비이다. 이 시험설비 중에서 가장 핵심적인 부분은 터보펌프의 구동력을 생성시키는 고온공기 생성시스템이다. 고압공기와 에탄올을 사용하는 알코올버너에 의해 시험시설에서 요구되는 유량과 온도가 생성된다. 본 연구에서는 국내기술로 제작한 알코올버너의 개발시험을 수행하였으며, 터보펌프 실매질 시험설비 구축에 앞서 버너의 제작기술과 운용경험을 확보할 수 있었다. 75톤급 터보펌프 실매질 시험에서는 이 알코올버너가 2기 동시 운용되어 터빈이 요구하는 구동력을 충족시킬 것으로 보인다.Key Words: Turbopump(터보펌프), Real-propellant Test Facility(실매질 시험설비), Alcohol Burner(알코올버너), High Pressure Air(고압공기), Ethanol(에탄올)

Characteristics of Dynamic Pressures in Liquid Rocket Thrust Chambers

The objective of this paper is to characterize dynamic pressure traces measured at various experimental conditions of liquid rocket thrust chambers. Stability rating test and self-excited combustion instability results for subscale and full-scale thrust chambers show various aspects of dynamic behavior of the pressure field depending on combustion system hardware and operating conditions. External perturbations facilitated by a shock wave generated from an explosion of solid material are able to alter the stable combusting flow to an unstable one when it has lack of dynamic stability margin. The direct comparison of pressure traces for self-excited and perturbed high frequency instabilities suggests that coupling mechanisms behind these two cases are totally different from each other. Naturally occurring combustion instability seems to be first coupled with a low frequency wave that affects flame more vigorously with the smaller phase difference between heat release rate and acoustics than a high frequency wave. However, for the artificial perturbation, the combusting flow triggered by a shock wave becomes located at physical conditions irrelevant to those before the perturbation.

Performance Test of A Reverse-Annular Type Combustor (TS2) for APU

Development of a small gas-turbine combustor for 100㎾ class APU(Auxiliary Power Unit) has been performed. This combustor is a reverse-annular type and has a tangential swiller in the liner head to improve the fuel/air mixing and flame stability. Three main and three pilot fuel injectors of the simplex pressure-swirl type are used. The performance target at the design condition includes a turbine inlet temperature of l170k, a combustion efficiency of 99%, a pattern factor of 30%, and an engine durability of 3000 hours. Under developing the combustor, we conducted the performance test of our first prototype(TS1) with some variants. As a result of the test, the performance targets of the combustor are satisfied except that the pattern factor is about 4% higher than the target value. Therefore, the second prototype(TS2) was redesigned and the performance test was conducted with the critical focus on the pattern factor and the exit mean temperature. We adopted TS2 four variants to check the improvement of the pattern factor. As a result, the pattern factors of several variants were satisfied with the performance target. Finally, the TS2A variant was chosen as a final combustor fur our APU model.

Human computer competition in game situation: motion planning for boxing

This paper presents a motion planner for robots in a game situation, in which the agents involved have conflicting goals. More specifically, a human-computer boxing game system is developed in a graphical environment. One boxer is controlled by a human through a motion tracking system, while the other is controlled by a motion planning algorithm. The planner has a defensive and an offensive strategies. The defensive strategy tries to move one of the forearms between the opponents fist and its body, while the offensive strategy locates an exposed part of the opponents body and throws a punch at it. To achieve an interactive operation, the motion planner considers only kinematic and geometric constraints during the search. This project is also aimed at integrating a planner with all actual robot, and investigating associated technological bottlenecks.

Pressure Control of Staged Combustion Liquid Rocket Engine

For the control of pre-burner combustion pressure, the open angle of TTR(Throttle for Thrust Regulation) valve was varied from 143° to 185° while testing of cold flow , ignition, combustion. The major performance variables of rocket engine and hydraulic performance of TTR valve regarding the open angle was verified. However the controllability of pre-burner combustion pressure was not verified due to the limitations of test. The comprehensive research will be done after supplementing these problems.

Performance Characteristics Under Non-Reacting Condition with Respect to Length of a Subscale Diffuser for High-Altitude Simulation

The performance characteristics of a subscale diffuser under non-reacting conditions for high-altitude simulation were numerically investigated with respect to different lengths of the secondary throat diffuser. The ratio of the length of the diffuser entrance to the nozzle exit diameter was set to 0, 50, and 100%. In addition, flow characteristics were studied for a range of length-to-diameter ratios of the secondary throat diffuser. An insufficient diffuser entrance length caused contraction of the plume immediately after the nozzle exit. When the length-to-diameter ratio was less than 8, a strong Mach disk was formed inside the diffuser, resulting in a sharp increase in pressure. In addition, flow characteristics in the diverging part of the diffuser were investigated for a range of diverging part lengths. A short diverging part may lead to abrupt pressure recovery, resulting in the possible application of mechanical load to the diffuser. Corresponding Author, khongjip@cnu.ac.kr 2014 The Korean Society of Mechanical Engineers C 정봉구 김홍집 전준수 고영성 한영민 · · · · 322 d 디퓨저 입구 : e 디퓨저 출구 : ne 노즐 출구 : o 작동조건 : s 아음속 디퓨저 : st 차목 디퓨저 : 2 * 노즐 목 :