Jin Ping

Scaling of the flowfield in a combustion chamber with a gas?gas injector

The scaling of the flowfield in a gas–gas combustion chamber is investigated theoretically, numerically and experimentally. To obtain the scaling criterion of the gas–gas combustion flowfield, formulation analysis of the threedimensional (3D) Navier–Stokes equations for a gaseous multi-component mixing reaction flow is conducted and dimensional analysis on the gas–gas combustion phenomena is also carried out. The criterion implies that the size and the pressure of the gas–gas combustion chamber can be changed. Based on the criterion, multi-element injector chambers with different geometric sizes and at different chamber pressures ranging from 3 MPa to 20 MPa are numerically simulated. A multi-element injector chamber is designed and hot-fire tested at five chamber pressures from 1.64 MPa to 3.68 MPa. Wall temperature measurements are used to understand the similarity of combustion flowfields in the tests. The results have verified the similarities between combustion flowfields under different chamber pressures and geometries, with the criterion applied.

Numerical and experimental study on shear coaxial injectors with hot hydrogen-rich gas/oxygen-rich gas and GH2/GO2

The influences of the shear coaxial injector parameters on the combustion performance and the heat load of a combustor are studied numerically and experimentally. The injector parameters, including the ratio of the oxidizer pressure drop to the combustor pressure (DP), the velocity ratio of fuel to oxidizer (RV), the thickness (WO), and the recess (HO) of the oxidizer injector post tip, the temperature of the hydrogen-rich gas (TH) and the oxygen-rich gas (TO), are integrated by the orthogonal experimental design method to investigate the performance of the shear coaxial injector. The gaseous hydrogen/oxygen at ambient temperature (GH2/GO2), and the hot hydrogen-rich gas/oxygen-rich gas are used here. The length of the combustion (LC), the average temperatures of the combustor wall (TW), and the faceplate (TF) are selected as the indicators. The tendencies of the influences of injector parameters on the combustion performance and the heat load of the combustor for the GH2/GO2 case are similar to those in the hot propellants case. However, the combustion performance in the hot propellant case is better than that in the GH2/GO2 case, and the heat load of the combustor is also larger than that in the latter case.

Experimental and Numerical Investigation of Large Mass Flow Rate Gas-Gas Injectors

†‡ This paper focuses on methodologies of investigation and design of large mass flow rate gas-gas injector. The experimental and CFD methods of GO2/GH2 single-element engine were presented at first. The combustor wall temperatures were measured using arrays of thermocouples instrumentation. The temperature increments along the axial direction had been obtained in experiments, which could indicate the general development and completion length of combustion. The combustion length shown in the results of numerical simulation of a typical shear coaxial injector at pressure of 3MPa and mass flow rate of 113g/s agreed with that of experiment. The typical CFD combustion flow field showed that the heat protection of shear-coaxial injector was well, but the combustion length was very long. The influences of key parameters on combustion were conducted, and the optimum-parameter shearcoaxial injector was designed and tested. The results of tests showed the optimum-parameter injector could obviously shorten the combustion length and the combustion was completed far before the throat at mass flow rate of 226g/s which was twice the mean mass flow rate of the SSME single main injector (SSMI). The results of CFD prediction showed that the optimum-parameter injector could undertake mass flow rate of 452g/s which was 4 times that of SSMI. The other new designs had been made based on studies of the shear-coaxial injector flow fields, and simulations and experiments were also conducted. The results showed that the O2 post expansion design could enhance the mixing and decrease the combustion length regardless of the expansion angle, H2 impinging design increased the combustion length, the 0.1mm thickness splitter plate rarely influenced the combustion length compared with 0.5mm, and the multi-hole design had a severe heat protection issue of injector faceplate.

Large Flow rate Shear-Coaxial Gas-gas Injector

Based on the previous results of studies in single-element condition, an optimal design single-element GO2/GH2 injector was designed and tested at a large flow rate condition firstly, and the result shows that this injector can complete combustion in the nominal combustor. Furthermore, to investigate the combustion characteristics of large flow rate injector in the multi-element injector chamber which have the interaction between the elements, an optimal design multi-element shear mixing injector equipped with seven elements was deigned. The shear mixing element had high H2/O2 velocity ratio and flared O2 post tip. Numerical simulation and repeat hot-fire tests were carried out with the injector. Steady operations were obtained without any stability aids, and the injector showed benign heat environments on the faceplate and cylinder wall. The combustion efficiency of this injector exceeds 99% in the flow rate of 3.7 times than that of SSME main injection element in the nominal combustor. Nomenclature C p = chamber pressure MR = mixing ratio m& = mass flow rate vr = velocity ratio 2 O v = O2 injection velocity 2 H pr = H2 pressure drop ratio, / C pp

Scaling study of the combustion performance of gas—gas rocket injectors

To obtain the key subelements that may influence the scaling of gas—gas injector combustor performance, the combustion performance subelements in a liquid propellant rocket engine combustor are initially analysed based on the results of a previous study on the scaling of a gas—gas combustion flowfield. Analysis indicates that inner wall friction loss and heat-flux loss are two key issues in gaining the scaling criterion of the combustion performance. The similarity conditions of the inner wall friction loss and heat-flux loss in a gas—gas combustion chamber are obtained by theoretical analyses. Then the theoretical scaling criterion was obtained for the combustion performance, but it proved to be impractical. The criterion conditions, the wall friction and the heat flux are further analysed in detail to obtain the specific engineering scaling criterion of the combustion performance. The results indicate that when the inner flowfields in the combustors are similar, the combustor wall shear stress will have similar distributions qualitatively and will be directly proportional to pc0.8dt−0.2 quantitatively. In addition, the combustion peformance will remain unchanged. Furthermore, multi-element injector chambers with different geometric sizes and at different pressures are numerically simulated and the wall shear stress and combustion efficiencies are solved and compared with each other. A multielement injector chamber is designed and hot-fire tested at several chamber pressures and the combustion performances are measured in a total of nine hot-fire tests. The numerical and experimental results verified the similarities among combustor wall shear stress and combustion performances at different chamber pressures and geometries, with the criterion applied.